Russia and Ukraine met online for their fourth round of talks on Monday while Russian forces continued airstrikes on the Ukrainian capital Kyiv and the southern port city of Mariupol.

The airstrikes, which killed two people and injured at least a dozen, according to Ukraine's emergency services, came as the Russian military edged closer to Kyiv and kept up its siege of Mariupol, where officials said nearly 2,200 people have been killed in the fighting.

"As of 07:40, the bodies of two people were found in a nine-story apartment building, three people were hospitalized and nine people were treated on the spot," the country's emergency services said on Facebook, adding that the building was in Kyiv's Obolon district.

Meanwhile, separatists in eastern Ukraine said on Monday that a strike by Kyiv's forces in Donetsk had left at least 20 people dead.

Rebel officials said that fragments from a Ukrainian Tochka missile that had been shot down landed in the center of the city.

Kyiv's lead negotiator, Mykhailo Podolyak, placed conditions on continuing talks: "Peace, an immediate cease-fire and the withdrawal of all Russians troops－and only after this can we talk about regional relations and about political differences."

Ukrainian President Volodymyr Zelensky said the clear aim of his negotiators was to "do everything "to arrange for him to meet Russian President Vladimir Putin.

"We must hold on. We must fight. And we will win," Zelensky said in a video speech.

Zelensky renewed on Monday his call for NATO to impose a no-fly zone, after an attack near the western city of Lviv.

Talks between Kyiv and Moscow have yet to yield a cease-fire and the Russian offensive has shown no signs of easing.

But Leonid Slutsky, a senior member of Russia's negotiating team, said that "significant progress" had been made at the earlier talks, adding that the delegations could possibly soon reach draft agreements.

Meanwhile, energy officials in Kyiv said the electricity supply had been restored at Ukraine's retired Chernobyl nuclear power plant.

Power had been cut to the site of the world's worst nuclear disaster, but the UN's atomic energy watchdog said there was "no critical impact to safety".

Separately, a US journalist was killed on Sunday as fighting escalated in Kyiv's suburbs－the first foreign reporter to die since Russia's "special military operation "started on Feb 24.