Ukraine and its allies expressed fury on Friday after Europe's largest atomic power plant was attacked and seized by invading Russian forces, which continued to shell major cities.

The six reactors at Zaporizhzhia, which can power up to four million homes, appeared undamaged by the fighting and a fire that broke out in a training facility.

Kyiv is sending a delegation to Thursday's ceasefire talks, but has warned it will not accept 'ultimatums'
Kyiv is sending a delegation to Thursday's ceasefire talks, but has warned it will not accept 'ultimatums' AFP / Sergey BOBOK

But Kyiv accused the Kremlin of "nuclear terror", and US envoy to the United Nations Linda Thomas-Greenfield said the attack was "incredibly reckless and dangerous".

Moscow's UN ambassador called accusations that Russian forces had shelled the plant part of "an unprecedented campaign of lies".

According to Ukraine, thousands of civilians have died since President Vladimir Putin's military invaded on February 24, claiming to be fighting a Western-leaning "Nazi" threat on its border.

A Ukrainian man stands in the rubble in Zhytomyr following a Russian missile strike
A Ukrainian man stands in the rubble in Zhytomyr following a Russian missile strike AFP / Emmanuel DUPARCQ

In a Kyiv hospital, wounded soldiers told AFP of their grim battle against the Russian advance on the capital, and vowed to return to the frontline.

"We were on reconnaissance and came across an enemy column that had made a breakthrough," said Motyka, 29, who was hit by shrapnel on his right side.

After the fall of a first major Ukrainian city to Russian forces, Putin appeared in no mood to heed a global clamour for hostilities to end
After the fall of a first major Ukrainian city to Russian forces, Putin appeared in no mood to heed a global clamour for hostilities to end AFP / Aris Messinis

"We fought them and killed their soldiers on foot, but they showered us with mortar fire."

On Friday, missile and bomb attacks on cities continued, the Ukrainian military said on Facebook, adding that the main focus of Russian troops was to encircle Kyiv.

It added that Russian artillery and multiple launch rocket systems were pounding residential buildings and infrastructure.

Ukrainian authorities said residential and other areas in the eastern city of Kharkiv had been 'pounded all night' by indiscriminate shelling
Ukrainian authorities said residential and other areas in the eastern city of Kharkiv had been 'pounded all night' by indiscriminate shelling AFP / Sergey BOBOK

President Volodymyr Zelensky said the attack at the nuclear plant "could have stopped the story, the history of Ukraine, the history of Europe."

"Russian tank commanders knew what they were firing at," he said, adding: "The terrorist state now resorted to nuclear terror."

Part of a rocket following apparent shelling by Russian forces in Ukraine's second-biggest city of Kharkiv
Part of a rocket following apparent shelling by Russian forces in Ukraine's second-biggest city of Kharkiv AFP / Sergey BOBOK

Zelensky will address the US Senate via Zoom on Saturday at the request of Kyiv, a US legislative aide said.

As the war intensifies, some US lawmakers are urging President Joe Biden to take a tougher stance against Russia, such as by suspending imports of its oil.

Ukrainian President Volodymyr Zelensky speaks during a press conference in Kyiv on March 3, 2022
Ukrainian President Volodymyr Zelensky speaks during a press conference in Kyiv on March 3, 2022 AFP / Sergei SUPINSKY

"We are faced together with what is President Putin's war of choice, unprovoked, unjustified, and a war that is having horrific, horrific consequences," US Secretary of State Antony Blinken said in Brussels.

Ukrainian soldiers near Kyiv
Ukrainian soldiers near Kyiv AFP / Aris Messinis

"We're committed to doing everything we can to make it stop."

With fears growing of nuclear conflict, the US and Russian armed forces have set up a new direct phone line to reduce the risks of "miscalculation," the Pentagon said Friday.

But Putin has been unmoved as Russia has become an economic, sporting and cultural pariah.

Map of Ukraine locating areas where explosions, strikes and fighting have been reported and under Russian control, with additional information as of Feb 26, 0630 GMT
Map of Ukraine locating areas where explosions, strikes and fighting have been reported and under Russian control, with additional information as of Feb 26, 0630 GMT AFP / Kenan AUGEARD

According to the Kremlin, Putin told his Belarusian counterpart that "the tasks set for the (Ukraine) operations are going according to plan and will be fulfilled in their entirety".

Kremlin spokesman Dmitry Peskov called on Russians "to unite around our president", after thousands braved mass arrests at anti-war demonstrations this week.

Ukrainian civilians in Irpin on the western edge of Kyiv saw they homes go up in flams as Russian forces shelled residential areas
Ukrainian civilians in Irpin on the western edge of Kyiv saw they homes go up in flams as Russian forces shelled residential areas AFP / Aris Messinis

Authorities have imposed a news blackout and two liberal media groups have halted operations.

Multiple media websites, including the BBC, were partially inaccessible in Russia.

Twitter was restricted and Facebook blocked.

The BBC and Bloomberg said they were suspending work in Russia after lawmakers in Moscow approved legislation to impose fines and jail terms of up to 15 years for anyone publishing "fake news" about the army.

CNN said it would halt broadcasting in Russia, while independent Russian newspaper Novaya Gazeta said it would remove Ukraine content in the wake of the new law.

Russia has intensified strikes across Ukraine with fresh reports of civilian casualties and devastating damage, particularly in southern areas near Kherson, the first city to fall to Moscow's troops.

NATO, fearful of provoking its own war with nuclear-armed Russia, again ruled out enforcing a no-fly zone over Ukraine.

Zelensky bitterly slammed NATO saying it had given "the green light for further bombing of Ukrainian cities and villages."

Mariupol, east of Kherson, is cut off without water or electricity in the depths of winter.

The port city's deputy mayor Sergei Orlov told BBC radio that its situation was "terrible" after 40 hours of shelling of sites including schools and hospitals.

"I believe that (Putin) wants to destroy Ukraine as a nation," he said.

In the northern city of Chernihiv, 47 people died Thursday when Russian forces bombed residential areas, including schools and a high-rise apartment block, according to a new toll given by local officials.

Putin has denied bombing cities.

Ukraine authorities say residential parts of the eastern city of Kharkiv have also come under indiscriminate shelling, which UN prosecutors at The Hague are investigating as a possible war crime.

Ukraine's Foreign Minister Dmytro Kuleba demanded a special tribunal, alleging there were "numerous cases of, unfortunately, when Russian soldiers rape women in the Ukrainian cities".

In Geneva, the UN Human Rights Council overwhelmingly voted to create a top-level investigation into violations committed in the invasion.

"The message to Putin has been clear: you're isolated on a global level and the whole world is against you," Ukrainian ambassador Yevheniia Filipenko said after the vote.

The UN Security Council will also hold an emergency meeting Monday on the humanitarian crisis triggered in Ukraine by the Russian invasion and discuss a possible draft resolution, diplomats told AFP Friday.

The UN says more than 1.2 million refugees have flooded into neighbouring countries from Ukraine.

"The bullets and bombs in Ukraine could take the global hunger crisis to levels beyond anything we've seen before," said agency director David Beasley.