Ukraine's Zelensky dismisses Russian claims of scaleback

Ukrainian President Volodymyr Zelensky on Wednesday dismissed Russia's vows to de-escalate fighting against its neighbour, saying his army was getting ready for further fighting in the east.

"We don't believe anyone, not a single beautiful phrase," Zelensky said in a video address to the nation, adding that Russian troops were regrouping to strike the eastern Donbass region.

"We will not give anything away. We will fight for every metre of our territory," he added.

After another round of peace talks in Istanbul on Tuesday, a Russian negotiator said Moscow would "radically" scale back its attacks around the capital Kyiv and the northern city of Chernigiv.

However, shelling continued during the night.

On Wednesday, US military officials said Russian forces did begin to pull out of the defunct Chernobyl nuclear power site north of Kyiv.

"We think that they are leaving, I can't tell you that they're all gone," said a US defence official speaking on condition of anonymity.

Zelensky said in his video address that any retreat by Russian forces was "the result of the work of our defenders."

Zelensky said that as the centre for the global fight for freedom, Ukraine has the right to demand weapons from the international community, including tanks, planes, artillery systems.

"Freedom must be armed as well as tyranny," he said.

In a separate development, the Russian defence ministry announced a local ceasefire Thursday to allow civilians to be evacuated from Ukraine's port of Mariupol, which has been under siege for weeks, left without water, food and power.

Fighting raged Wednesday in Ukraine despite Russia's indication that it planned to de-escalate, and US intelligence claimed Kremlin leader Vladimir Putin is angry after being misled by his own military.

Hopes that negotiations in Istanbul could open the door to relative calm in pro-Western Ukraine evaporated in a series of battles, including more Russian bombing of civilian areas and advances by Ukrainian fighters.

As the number of refugees estimated by the United Nations topped four million  -- close to one in 10 inhabitants -- there was no sign of Russia making good on its promise during the talks Tuesday to pull back from the city of Chernigiv and capital Kyiv.

A reporter heard frequent explosions coming from the direction of the strategic town of Irpin to the northwest of Kyiv.