Russia squeezes Kyiv as 'unimaginable' tragedy looms in Ukraine

Russian forces inched towards Kyiv and pounded civilian areas in other Ukrainian cities Friday, drawing warnings of "unimaginable tragedy" as the United States and the EU moved to tighten the economic noose around the Kremlin.

Sixteen days after Moscow shocked the world by invading Ukraine, the United Nations and others said it may be committing war crimes in cities such as Mariupol, which for days now has been besieged by Vladimir Putin's forces.

On Friday officials in the southern port said more than 1,500 people had been killed during 12 days of attacks.

Survivors have been trying to flee Russian bombardment in a freezing city left without water or heating, and running out of food. The situation is "desperate," a Doctors Without Borders official said.

"Hundreds of thousands of people... are for all intents and purposes besieged," Stephen Cornish, one of those heading the medical charity's Ukraine operation, said in an interview.

"Sieges are a medieval practice that have been outlawed by the modern rules of war for good reason."

As Russia widens its bombardment and talks between Moscow and Kyiv seemingly go nowhere, Ukrainian President Volodymr Zelensky's pleas for NATO to intervene have grown increasingly desperate.

US President Joe Biden on Friday again ruled out direct action against nuclear-armed Russia, warning that it would lead to "World War III."

Instead Washington added more layers of sanctions to those already crippling Russia's economy, this time ending normal trade relations and announcing a ban on signature Russian goods vodka, seafood and diamonds. 

The United States and the European Union also suspended the export of their luxury goods to Russia.