AKIPRESS.COM - More than 30 people were killed in a “criminal” blaze in Ukraine's southern city of Odessa, as violence spread across the country during the bloodiest day since Kiev's Western-backed government took power, Haveeru reported today.

Ukraine's interior ministry said at least 31 people had died in the fire Friday, with local media reporting that local protesters were believed to have been in the burning building at the time.

Most of those who were killed died from smoke inhalation, while others perished trying to escape by jumping out of windows. Russia said it was “outraged” as the port city became a new front in an escalating months-long crisis.

The foreign ministry in Moscow called on Ukraine and its “Western backers to end the anarchy and take responsibility before the Ukrainian people,” blaming Kiev's “criminal irresponsibility” for the sinister turn of events.

It capped a day of violent clashes between pro-Russian and pro-Ukrainian militants, with reports of renewed fighting in Slavyansk leading to the deaths of two more Ukrainian soldiers, meaning at least nine people had been killed in violence in the flashpoint eastern town throughout the day.

Meanwhile, U.S. President Barack Obama threatened to expand punitive sanctions to broad sections of the Russian economy if Moscow continued to foment chaos in the former Soviet republic ahead of planned May 25 presidential elections.

“If in fact we see the disruptions and the destabilization continuing so severely that it impedes elections on May 25, we will not have a choice but to move forward with additional... severe sanctions,” Obama said at a joint news conference with German Chancellor Angela Merkel.

Previously, the administration had said such measures would only come into force if Russia sent its troops over the border.

In a sign of worsening relations, U.S. Secretary of State John Kerry announced he was postponing a phone call with Russian Foreign Minister Sergei Lavrov.

And while Obama was speaking at the White House, an emergency meeting of the UN Security Council took place at Russia's request to complain about the Ukrainian army's assault on Slavyansk – an attempt by Kiev's interim rulers to grab back the initiative from pro-Moscow rebels.

The Kremlin – which has denied links to rebels who have taken over buildings in dozens of towns and cities in Ukraine's east – said the raid was “leading Ukraine towards catastrophe” and pronounced dead the peace deal struck in Geneva last month.