Zelensky asks for 'maximum' sanctions for Russia to stop war in Ukraine

May 23 (UPI) -- As Russian forces kept up attacks in eastern Ukraine on Monday, Ukrainian President Volodymyr Zelensky told world leaders that allies must ratchet up economic sanctions against Moscow to put a stop to its military aggression.

Speaking remotely to the World Economic Forum in Davos, Switzerland, Zelensky asked global leaders for "maximum" economic punishment against Russian President Vladimir Putin's government -- including sanctions for Russian-produced oil, blocking Russian banks and isolating the country on trade.

Zelensky also asked for help in creating a humanitarian corridor in the Black Sea to facilitate food shipments. The Ukrainian leader said that current Russian blockades are causing a food crisis.

"Ukraine is short on time," he said according to The Washington Post. "This year, the words 'turning point' are to become more than just a rhetorical phrase."

Economically, Zelensky said that Ukraine has seen hundreds of billions of dollars in losses since the start of the fighting in February, and stressed that Ukrainian forces could negate Russia's military advantage if it had more long-range weapons from the West.

The United States and other Western nations have given billions in aid to Ukraine over the past three months, including military hardware and humanitarian aid.

David Beasley, the head of the United Nations World Food Program, said at the forum Monday that Russian blockades must be broken at Ukraine's ports. Failing to do so, he said, amounts to "a declaration of war on global food security."

Meanwhile on Monday, Russian soldiers attacked the eastern city of Severodonetsk as Moscow looks for a breakthrough in its push to dominate Ukraine's eastern region, which is populated with many pro-Russia separatists. Russia has been focusing more in recent weeks on controlling Ukraine's eastern Luhansk and Donetsk regions, collectively known as the Donbas.

Luhansk regional leader Serhiy Haidai said that Russia has been shelling the area regularly over the past week. Zelensky said over the weekend that Ukrainian forces in the region have been holding strong against Russian troops.

"Every day they are trying to break the line of defense," Haidai said, according to The Washington Post. "Round-the-clock there is shelling, and unfortunately the Russian army chose the scorched earth tactic against the city of Severodonetsk.

"They are simply systematically destroying the city. Everywhere is being shelled constantly."

Haidai also accused Russian forces of firing into residential areas, a claim that's been made against Moscow's military virtually since the first day of the war. A Russian soldier was sentenced to life in prison on Monday for killing a 62-year-old Ukrainian man in the early days of the fighting. His was the first war crimes trial linked to Russia's invasion.

Denis Pushilin, leader of the Russian-backed Donetsk People's Republic, said on Monday that a tribunal was being assembled to try Ukrainian soldiers from the Azovstal steel plant in Mariupol as possible war criminals.

Ukrainian troops had taken refuge at the plant for weeks while fending off Russian troops there until most of the remaining ones began to surrender last week. Russian military officials have claimed that more than 2,000 Ukrainian troops had surrendered there.

Russian Deputy Foreign Minister Sergey Rudenko said that Moscow is open to a possible prisoner exchange involving the soldiers at the Mariupol plant.