Russia's military will hold fire and open humanitarian corridors in several Ukrainian cities on Monday, the Defence Ministry said, after fighting halted weekend evacuation efforts and civilian casualties from Russia's invasion mounted.

The corridors were to be opened at 10am Moscow time (0700 GMT) from the capital Kyiv as well as the cities of Kharkiv, Mariupol and Sumy and are being set up at the personal request of French President Emmanuel Macron, the ministry said.

According to maps published by the RIA news agency, the corridor from Kyiv will lead to Russian ally Belarus, and civilians from Kharkiv will only have a corridor leading to Russia. Corridors from Mariupol and Sumy will lead both to other Ukrainian cities and to Russia.

Those who want to leave Kyiv will also be able to be airlifted to Russia, the ministry said, adding it would use drones to monitor the evacuation.

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

'Town mayor killed by Russian fire'

Meanwhile, Russian forces have killed the mayor of Gostomel, a town near the Ukrainian capital Kyiv that is home to a strategic airport, AFP quoted the city authorities as saying.

“The head of Gostomel, Yuri Illich Prylypko, died while distributing bread to the hungry and medicine to the sick,” the city said on its Facebook page.

Prylypko was shot dead along with two others, it said, without specifying when.

“No-one forced him to go under the occupiers' bullets,” it said. “He died for his people, for Gostomel. He died a hero.”

Gostomel, northwest of Kyiv, is home to the strategic Antonov military airport, which was the site of fierce battles between Ukrainian and Russian forces in the first days of the war.

Russia's invasion has been condemned around the world, sent more than 1.5 million Ukrainians fleeing abroad, and triggered sweeping Western-led sanctions aimed at crippling the Russian economy.

Russia calls the campaign it launched on February 24 a "special military operation". It has repeatedly denied attacking civilian areas and says it has no plans to occupy Ukraine.

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 seven per cent of global supply.

Japan, which counts Russia as its fifth-biggest supplier of crude oil, is also in discussion with the United States and European countries about possibly banning Russian oil imports, Kyodo News reported on Monday.

Europe relies on Russia for crude oil and natural gas but has become more open to the idea of banning Russian products, a source familiar with the discussions told Reuters.

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

Read more: Why Russian military hasn’t had smooth sailing in Ukraine, yet

About 200,000 people remained trapped in the besieged Black Sea port of Mariupol, most sleeping underground to escape more than six days of shelling by Russian forces that has cut off food, water, power and heating, according to the Ukrainian authorities.

About half of the 400,000 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.

Ukrainian authorities said on Monday the southern city of Mykolayiv was being shelled.

'Arc of autocracy'

The civilian death toll from hostilities across Ukraine since Russia launched the invasion was 364, including more than 20 children, the United Nations said on Sunday, adding that hundreds were wounded.

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

Ukrainian President Volodymyr Zelensky warned Russians who committed atrocities against civilians they would face punishment.

"For you, there will be no peaceful place on this earth, except for the grave," he said in a televised evening address.

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.

Blinken said the United States was considering how it could backfill aircraft for Poland if it decided to supply its warplanes to Ukraine.

Putin says he wants a "demilitarised", "denazified" and neutral Ukraine, and on Saturday likened Western sanctions "to a declaration of war".

New Zealand became the latest country on Monday to announce it will impose sanctions on Russia, including a plan to stop superyachts, ships and aircraft from entering its waters or airspace.

South Korea toughened its financial sanctions against Russia by banning transactions with Russia's central bank.

Australian Prime Minister Scott Morrison urged China to act on its declarations of promoting world peace and join the effort to stop Russia's invasion of Ukraine, warning that the world was in danger of being reshaped by an "arc of autocracy".

"No country will have a bigger impact on concluding this terrible war in Ukraine than China," Morrison said in response to a question after a speech at the Lowy Institute think tank.

Western sanctions have pushed many companies to exit investments in Russia, while some Russian banks have been shut out of global financial payment systems, driving down the rouble and forcing Moscow to jack up interest rates.

On Sunday, more companies cut ties with Russia: American Express Co, Netflix Inc, accounting giants KPMG and PwC, and video sharing app TikTok.

But Chinese firms are staying put.