KYIV, Ukraine (AP) — Talks to stop the fighting in Ukraine resumed Friday, as another desperate attempt to rescue civilians from the shattered and encircled city of Mariupol failed and Russia accused the Ukrainians of launching a helicopter attack on a fuel depot on Russian soil.

The governor of Russia's Belgorod region, Vyacheslav Gladkov, said a fiery cross-border raid by two helicopter gunships left two people wounded, though state oil company Rosneft denied anyone was hurt.

"Certainly, this is not something that can be perceived as creating comfortable conditions for the continuation of the talks," Kremlin spokesman Dmitry Peskov said, five weeks after Moscow began sending upwards of 150,000 of its own troops across Ukraine's border.

The Russian claim could not immediately be verified, and Ukraine denied responsibility.

"For some reason they say that we did it, but in fact this does not correspond with reality," Oleksiy Danilov, secretary of Ukraine's national security council, said on Ukrainian television.

Russia has reported cross-border shelling from Ukraine before, including an incident last week that killed a military chaplain, but not an incursion of its airspace. The Rosneft depot is about 35 kilometers (21 miles) from the Ukraine border.

Meanwhile, Russia continued withdrawing some of its troops from areas around Kyiv, three days after Moscow said it would reduce military activity near the Ukrainian capital and the northern city of Chernihiv to promote trust at the bargaining table.

While Russian forces kept up their bombardment of those two zones, Ukrainian troops exploited the pullback on the ground by mounting counterattacks and retaking a number of towns and villages.

Still, Ukraine and its allies warned that the Kremlin is not de-escalating but resupplying its troops and shifting them to the country's east for an intensified assault on the mostly Russian-speaking Donbas region, which includes Mariupol.

The latest negotiations, which took place by video, followed a meeting Tuesday in Turkey, where Ukraine reiterated its willingness to abandon a bid to join NATO and declare itself neutral — Moscow's chief demand. In return, Ukraine proposed that its security be guaranteed by several other countries.

The head of the Russian delegation, Vladimir Medinsky, said on social media that Moscow's positions on retaining control of the Crimean Peninsula — seized from Ukraine in 2014 — and expanding the territory in eastern Ukraine held by Russia-backed separatists "are unchanged."

The invasion has left thousands dead and driven more than 4 million refugees from Ukraine.

On the outskirts of Kyiv, where Russian troops have withdrawn, damaged cars lined the streets of Irpin, a suburban area popular with young families, now in ruins. Emergency workers carried elderly people on stretchers over a wrecked bridge to safety.

Three wooden crosses next to a residential building that was damaged in a shelling marked the graves of a mother and son and an unknown man. A resident who gave her name only as Lila said she helped hurriedly bury them on March 5, just before Russian troops moved in.

"They were hit with artillery and they were burned alive," she said.

An Irpin resident who gave his name only as Andriy said the Russians packed up their equipment and left on Tuesday. The next day, they shelled the town for close to an hour before Ukrainian soldiers retook it.

"I don't think this is over," Andriy said. "They will be back."

To the south, the International Committee for the Red Cross said it was unable to carry out an operation to bring civilians out of Mariupol by bus. It said a team had been on its way but had to turn back.

City authorities said the Russians were blocking access to Mariupol.

"We do not see a real desire on the part of the Russians and their satellites to provide an opportunity for Mariupol residents to evacuate to territory controlled by Ukraine," Petro Andryushchenko, an adviser to the mayor of Mariupol, wrote on the Telegram messaging app.

He said Russian forces "are categorically not allowing any humanitarian cargo, even in small amounts, into the city."

The strategic port city on the Sea of Azov has seen some of the worst suffering of the war, with weeks of heavy fighting and shortages of water, food, fuel and medicine. Around 100,000 people are believed left in the city, down from a prewar 430,000.

"We are running out of adjectives to describe the horrors that residents in Mariupol have suffered," Red Cross spokesperson Ewan Watson said.

On Thursday, Russian forces blocked a 45-bus convoy attempting to evacuate people from Mariupol, and only around 600 people were able to leave in private cars, the Ukrainian government said. Russian forces also seized 14 tons of food and medical supplies bound for Mariupol, Deputy Prime Minister Iryna Vereshchuk said.

In other developments Friday, Ukrainian President Volodymr Zelenskyy's office said 86 Ukrainian service members were freed in the Zaporizhzhia region as part of a prisoner swap with Russia. The number of Russians released was not disclosed.

Over the past week, the Kremlin, in a seeming shift in its war aims, said its "main goal" is gaining complete control of the Donbas.

The Donbas is the industrial region of eastern Ukraine where Moscow-backed separatists have been battling Ukrainian forces since 2014. The separatists have declared two areas independent republics.

Mariupol's capture, in particular, would be a major prize for the Russians, giving them an unbroken land bridge to Crimea.

Amid the Russian pullback on the ground and its continued bombardment, Ukraine's military said it had retaken 29 settlements in the Kyiv and Chernihiv regions.

Russian forces in the northeast also continued to shell Kharkiv, and in the southeast sought to seize the cities of Popasna and Rubizhne as well as Mariupol, the Ukrainian military said.

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Karmanau reported from Lviv, Ukraine. Andrea Rosa in Irpin, Ukraine, and Associated Press journalists around the world contributed to this report.

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Follow the AP's coverage of the war at https://apnews.com/hub/russia-ukraine