Russia has declared a partial ceasefire to allow humanitarian corridors out of the Ukrainian cities of Mariupol and Volnovakha, the Kremlin's defence ministry says.
"From 10am Moscow time (6pm AEDT), the Russian side declares a ceasefire and the opening of humanitarian corridors to allow civilians to leave Mariupol and Volnovakha," Russian news agencies quoted the defence ministry as saying.
In Mariupol, citizens would be allowed to leave during a five-hour window, it quoted the city's officials as saying.
At the time of publishing, there was no immediate confirmation that firing had stopped and it was not clear if the ceasefire would be extended to other areas, or how long it would last.
Earlier in the day, Russia blocked Facebook and some other websites and passed a law to allow much stronger powers to crack down on independent journalism, prompting the BBC, Bloomberg and other foreign media to suspend reporting in the country.
Ten days of fighting in Ukraine has created more than a million refugees, a barrage of sanctions that are increasingly isolating Moscow, and fears in the West of a wider global conflict that has been unthought-of for decades.
Moscow says its invasion is a "special operation" to capture individuals it regards as dangerous nationalists and has denied targeting civilians.
Ukraine says Russian forces have focused efforts on encircling Kyiv and Kharkiv, the country's second-biggest city, while aiming to establish a land bridge to Crimea.
Kyiv, in the path of a Russian armoured column that has been stalled outside the Ukrainian capital for days, came under renewed assault, with explosions audible from the city centre.
Russian forces have also encircled and shelled the strategic southeastern port city of Mariupol. There is no water, heat or electricity and food is running out, according to Mayor Vadym Boychenko.
"We are simply being destroyed," he said.
Russia cracks down on Facebook and other websites
President Vladimir Putin's actions have drawn almost universal condemnation, and many countries have imposed heavy sanctions.
Fighting back in the information war, Russia's parliament on Friday passed a law imposing a prison term of up to 15 years for spreading intentionally 'fake' news about the military.
"This law will force punishment - and very tough punishment - on those who lied and made statements which discredited our armed forces," Vyacheslav Volodin, the chairman of the Duma, Russia's lower house of parliament, said.
Russia is blocking Facebook for restricting state-backed channels, and the websites of the BBC, Germany's Deutsche Welle and Voice of America, among others.
The US is weighing cuts to imports of Russian oil and ways to minimise the impact on global supplies and consumers as politicians fast-track a bill that would ban Russian energy imports.
At a meeting on Friday, NATO rejected Ukraine's appeal for no-fly zones, saying they were increasing support but that stepping in directly could make the situation worse.
"We have a responsibility ... to prevent this war from escalating beyond Ukraine because that would be even more dangerous, more devastating and would cause even more human suffering," NATO Secretary-General Jens Stoltenberg said.
Friday's attack on the Zaporizhzhia nuclear power plant, the largest in Europe, about 230km west of Mariupol, brought the conflict to a perilous point, but officials later said the facility was safe.
US ambassador to the UN Linda Thomas-Greenfield said the world had narrowly avoided a nuclear catastrophe.
Bombing has worsened in recent days in the northeast cities of Kharkiv and Chernihiv, while Ukrainian presidential adviser Oleksiy Arestovych said an advance on the southern port of Mykolayiv had been halted.
If captured, the city of 500,000 people would be the biggest yet to fall.
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