The announcement came after two days of failed ceasefires to let civilians flee the besieged city of Mariupol, where hundreds of thousands of people are trapped without food and water, under relentless bombardment and unable to evacuate their wounded.

The new "corridors" would be opened at 10am Moscow time on Monday from the capital Kyiv and the eastern cities of Kharkiv and Sumy, as well as Mariupol, Russia's defence ministry said.

According to maps published by the RIA news agency, the corridor from Kyiv would lead to Belarus, while civilians from Kharkiv would be permitted to go only to Russia. Russia would also mount an airlift to take Ukrainians from Kyiv to Russia, the ministry said.

"Attempts by the Ukrainian side to deceive Russia and the whole civilised world ... are useless this time," the ministry said.

A spokesperson for Ukrainian President Volodymyr Zelenskiy called the move "completely immoral" and said Russia was trying to "use people's suffering to create a television picture".

"They are citizens of Ukraine, they should have the right to evacuate to the territory of Ukraine," the spokesperson told Reuters.

"This is one of the problems that is causing the humanitarian corridors to break down. They seem to agree to them, but they themselves want to supply humanitarian aid for a picture on TV, and want the corridors to lead in their direction."

Russia's invasion has been condemned around the world, sent more than 1.5 million Ukrainians fleeing abroad, and triggered sweeping sanctions that have isolated Russia to a degree never before experienced by such a large economy.

Russia denies deliberately targeting civilians. It calls the campaign it launched on February 24 a "special military operation" to disarm Ukraine and remove leaders it calls neo-Nazis. Ukraine and its Western allies call this a transparent pretext for an invasion to conquer a nation of 44 million people.

Oil prices soared to their highest levels since 2008 in Asian trade after the Biden administration said it was exploring banning imports of Russian oil.

Russia provides 7 per cent of global supply and even though the United States is not a major consumer of Russian crude such a ban would ripple through world markets.

The general staff of Ukraine's armed forces said Russian forces were "beginning to accumulate resources for the storming of Kyiv", a city of more than 3 million, after days of slow progress in their main advance south from Belarus.

While Russia's advance in the north on Kyiv has been stalled for days with an armoured column stretching for miles along a highway, it has made more progress in the south, pushing east and west along the Black and Azov Sea coasts.

In Mariupol, residents still trapped are sleeping underground to escape more than six days of shelling by Russian forces that has cut off food, water, power and heating.

About half of the people in the city were due to be evacuated on Sunday, but that effort was aborted for a second day when a ceasefire plan collapsed as the sides accused each other of failing to stop shooting and shelling.

Kherson is so far the only major city that Russians have captured. Ukraine said it had destroyed 30 Russian helicopters at an airfield there overnight. This could not be confirmed.

The official UN civilian death toll from hostilities across Ukraine is 364, including more than 20 children, though officials acknowledge this probably represents a fraction of the true toll.

Russia has acknowledged nearly 500 deaths among its soldiers. Ukraine says the true toll is many thousands. Death tolls cannot be verified, but footage widely filmed across Ukraine shows burnt-out wreckage of Russian armoured columns and Ukrainian cities reduced to rubble by Russian strikes.

US Secretary of State Antony Blinken said the United States had seen credible reports of deliberate attacks on civilians and was documenting them to support a potential war crimes investigation.

As anti-war protests took place around the world, Ukraine renewed its appeal to the West to toughen sanctions and also requested more weapons, including Russian-made planes.

Australian Associated Press