KYIV, Ukraine—A delegation led by Ukraine’s defense minister held cease-fire talks on Monday with Russian officials in Belarus as Russian forces shelled two residential neighborhoods in the eastern city of Kharkiv, killing at least 10 civilians, and Ukrainian defenders repelled attacks on the capital, Kyiv.

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KYIV, Ukraine—A delegation led by Ukraine’s defense minister held cease-fire talks on Monday with Russian officials in Belarus as Russian forces shelled two residential neighborhoods in the eastern city of Kharkiv, killing at least 10 civilians, and Ukrainian defenders repelled attacks on the capital, Kyiv.

The talks on the fifth day of Russia’s invasion of Ukraine come after Russian forces have struggled to make headway in most of the country, and failed so far to take any of Ukraine’s major cities as they faced fierce resistance. Russia was pouring large reinforcement convoys across the border on Monday, in what could be preparation for a renewed push on Kyiv and an attempt to besiege it.

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Russia, facing difficulties on the battlefield and under mounting economic sanctions, appears to be preparing a possible escalation of its war on Ukraine, even as diplomatic contacts aimed at stopping the fighting begin.

In an indication that Moscow may be shifting to a more destructive approach of targeting civilian areas, two residential neighborhoods of Kharkiv, Ukraine’s second-largest city, came under heavy shelling on Monday, likely by multiple rocket launchers.

At least 10 civilians were killed and more than 40 injured, with the toll likely to grow because continued shelling made it impossible for rescue workers to reach all the damaged areas, said Kharkiv Gov. Oleh Synehubov. “It’s a war crime,” he said. Most of Kharkiv’s residents are Russian-speakers, the population whose rights Moscow says it wants to protect through its military operation.

The chances of a cease-fire being agreed to at Monday’s talks were uncertain. Ukraine’s President Volodymyr Zelensky has demanded a full Russian withdrawal and a restoration of Ukraine’s territorial integrity.

Ukrainian Defense Minister Oleksii Reznikov, wearing a green baseball cap, arrived Monday for talks with Russian delegates in Belarus.

Photo: Sergei Kholodilin/Associated Press

Russian delegates sat opposite their Ukrainian counterparts at Monday’s talks in Gomel, Belarus.

Photo: Alexander Kryazhev/TASS/Zuma Press

Russia’s financial system is starting to feel the impact of Western sanctions imposed at the weekend. The ruble nosedived and Russia’s central bank raised its key interest rate to 20% to try to prevent an outflow of deposits from Russian banks as sanctions curb their access to international markets.

The U.S. and the European Union said at the weekend they would hinder Russia’s central bank from using its foreign reserves and exclude a number of Russian banks from the international Swift payments network, among other measures. The EU also closed its airspace to all Russian planes.

As additional Russian forces entered Ukraine, Kyiv continued to bolster its own military by mobilizing 100,000 new troops and arming its units with sophisticated new weaponry flowing in from the West.

Authorities in Kyiv, which was under curfew starting Saturday afternoon while Ukrainian forces engaged in firefights in several neighborhoods with Russian infiltrator units wearing civilian clothes or Ukrainian uniforms, allowed residents to move around on Monday morning. Long lines snaked around grocery stores and pharmacies as Kyivites patiently waited for their turn.

Outside one supermarket on the western side of Kyiv, the waiting time to enter was roughly two hours, even though many of the neighborhood’s residents have fled the city for the relative safety of western Ukraine. “We’re not going anywhere. I was born in Kyiv and I will die here,” said Valeria Voytenko, a 23-year-old post-office worker whose husband is fighting on the front lines of Kharkiv.

Russian forces faced heavy resistance in Ukraine and satellite images showed the extent of damage from combat. Delegations from Ukraine and Russia agreed to meet Monday, a day after Vladimir Putin said he had put his country’s nuclear forces on alert. Photo: Maxar Technologies The Wall Street Journal Interactive Edition

“If they had given us weapons, I would also go shoot them up and defend my home,” chimed in her friend Yana Kamun, a 20-year-old manicurist. “We will fight to the last one. And we have faith that Ukraine will win.”

The city was calm, with no looting or violence, as regular troops and volunteers with yellow armbands manned checkpoints at key intersections. Kyiv authorities warned that any looters would be shot on sight. In some areas, signs of intense fighting were visible: broken glass, a car with a bullet hole in its windshield, fragments of shells and grenades.

One of the volunteer troopers, 30-year-old Taras Oleksandovych, joined the new Territorial Defense force on Sunday, after a shootout with Russian infiltrators in his neighborhood of high-rise buildings on Kyiv’s western edge. “Neighborhood people gave us all this—old washing machines, tires, roofing, anything they could throw out of their windows—to create this barricade,” he said. “We will resist.”

Myroslav Malynovski, a construction worker, said he drove his family to western Ukraine as the war began but has now returned to Kyiv to help the military. When a Ukrainian T-64 tank on the western edge of the city broke down, he drove to the city center to find a welder to fix it, and brought camping gear, food and warm clothes for the tank’s crew.

A Ukrainian serviceman climbed into a tank outside Kyiv on Monday.

Photo: Manu Brabo for The Wall Street Journal

Sturdier tank traps, concrete blocks and orange garbage trucks blocked key roads. Electronic billboards that once advertised nightclubs, vacations in the Dominican Republic and sushi restaurants beamed black-and-white messages to the enemy. One, in central Kyiv, instructed Russian soldiers in vulgar language what to do with themselves.

On the front lines along the city’s northern and western edges, soldiers were buoyed by recent victories. “The famed Russian special forces came here, and ran away so fast that they left us three vehicles as trophies,” said a Ukrainian trooper as he readied to leave on a mission with a squad armed with sniper rifles.

In a sign that Russia doesn’t so far have control of the skies, convoys carrying Ukrainian reinforcements rumbled in broad daylight through the city, including several long-range artillery pieces followed by truckloads of shells.

“On the fifth day of the full-scale Russian war against the people of Ukraine, we’re standing firm,” Mr. Zelensky said Monday. “Every crime that the occupiers commit against us brings us closer and closer to each other. Russia never imagined that it would face such solidarity.”

While air-raid sirens sounded through the early hours of Monday, the intensity of Russian airstrikes was much lower than in previous nights.

In recent days Russian forces have cut off the main direct highway leading from Kyiv to the western city of Lviv. But connections between the capital and Lviv have remained open via central Ukraine and by train.

Ukrainian civilians from the Territorial Defense forces stood at a checkpoint in Kyiv on Monday.

Photo: Manu Brabo for The Wall Street Journal

Tires blocked a road at a checkpoint in Kyiv.

Photo: Manu Brabo for The Wall Street Journal

On Monday, Ukraine’s railways operated additional evacuation trains from Kyiv free of charge, on top of the previously scheduled connections to Lviv and other western Ukrainian cities. A large proportion of Kyiv’s population, which stood at three million people before the war began, has fled the city in the past five days.

Nikita Darnostup and Ulyana Panteleeva, both computer graphic designers, decided after watching the news on Monday morning that it was time to leave Kyiv while they still can. “We are getting ready for the worst,” said Mr. Darnostup, 28, as they waited for their train to Lviv outside Kyiv’s crowded main station. “We see that the situation is escalating, and it’s getting scarier and scarier.”

The couple previously fled their hometown of Donetsk, eastern Ukraine, in 2014 after Russian-backed forces seized it. “This is complete surrealism,” sighed Ms. Panteleeva, 27. “I never imagined we would have to go through this for a second time.”

Mr. Darnostup said, “I really want to believe that we will be able to see Kyiv again, one day.”

Russian President Vladimir Putin refused to take a call from Mr. Zelensky on the eve of Thursday’s invasion, which he said seeks to oust the Ukrainian government and “demilitarize” the country.

Russian officials said shortly after the war began that they would talk to Kyiv only once Ukrainian troops laid down their arms. Mr. Putin later urged the Ukrainian army to stage a coup against the country’s democratically elected president. The fact Moscow now seeks unconditional talks was celebrated by Ukrainian officials as an achievement for Ukraine and its armed forces.

Russia sent a delegation to the southern Belarusian city of Gomel on Sunday, but Mr. Zelensky initially said he refused to meet in a country that has become a launchpad for Russia’s attacks.

Mr. Zelensky did, however, speak by phone to Belarusian President Alexander Lukashenko later on Sunday, and said that he agreed to have his envoys meet with the Russian delegation on the river Prypiat along the Ukrainian-Belarusian border. Mr. Lukashenko pledged during the conversation, the two men’s first in two years, that no Russian military activity would be carried out from Belarus in the meantime, Mr. Zelensky said.

Ukrainians lined up Monday at the gate of a supermarket in Kyiv.

Photo: Manu Brabo for The Wall Street Journal

Kyiv residents on Monday were allowed to move around the city, which was under a curfew over the weekend.

Photo: Manu Brabo for The Wall Street Journal

The talks, held on the Belarusian side of the border with Ukraine, began shortly before 2 p.m. local time. “You can feel totally safe, this is our sacred duty,” Belarusian Foreign Minister Vladimir Makei told the Russian and Ukrainian delegations seated across from each other. “President Lukashenko earnestly hopes that ways for solving the crisis issues can be found during today’s talks, and all Belarusians pray for this.”

Because of continued fighting, the team sent by Mr. Zelensky had to travel to the talks on a circuitous route via Poland. The group includes the Ukrainian minister of defense, Oleksii Reznikov, and the majority leader in the Ukrainian parliament, David Arakhamia.

The Russian delegation includes presidential aide Vladimir Medinsky; Russia’s deputy ministers of defense and foreign affairs; Leonid Slutsky, the head of the International Committee of Russia’s State Duma; and Russia’s ambassador to Belarus, Boris Gryzlov, said Kremlin spokesman Dmitry Peskov.

A mother and her daughters reached the Polish border crossing of Medyka after a two-day, 300-mile journey from central Ukraine.

Photo: Dawid Zielinski for The Wall Street Journal

A group of medical students waited in Medyka on Sunday for a bus to the nearby Polish city of Przemysl.

Photo: Dawid Zielinski for The Wall Street Journal

Mr. Medinsky told Russian state news agency RIA that Russia’s representatives were ready for negotiations at any time. “Every hour for us is a saved life,” the agency cited him as saying.

In the five days of the offensive, Russia so far hasn’t seized any big Ukrainian city, and dozens if not hundreds of Russian troops have been taken prisoner, videos of them posted on social media so that their families in Russia could find out about their fate. Russia’s military on Sunday acknowledged for the first time that its forces suffered fatal casualties in Ukraine.

Moscow on Monday repeated its assertion that it has gone to war in Ukraine because Kyiv threatens Russia’s own security and accused it of attacking the residents of Ukraine’s eastern Donbas region, which has been under Russian control since 2014. Ukrainian and Western officials say these claims have no basis in reality.

“Russia did not start these hostilities, Russia is putting an end to them,” Defense Ministry spokesman Maj. Gen. Igor Konashenkov said in a video statement. “Hostilities by the regime in Kyiv and the systematic destruction of the inhabitants of Donbas lasted eight years. This needed to end. It was necessary to put an end to the endless threats from the Kyiv regime against Russia. And Russia will do that.”

In the Azov Sea town of Berdyansk, one of the handful that the Russian military currently controls, video footage broadcast by Ukrainian media showed dozens of residents protesting outside the city hall that now houses Russian occupation authorities. Waving Ukrainian flags, they chanted an obscene epithet to describe Mr. Putin, and “Glory to Ukraine.”

—Evan Gershkovich in Minsk contributed to this article.

Write to Yaroslav Trofimov at yaroslav.trofimov@wsj.com