Canada closed its embassy in Kiev on Wednesday after fierce clashes left at least 26 people dead in Ukraine, where anti-government protesters were locked in a stand-off with riot police.

"As a security precaution, and to ensure the protection of all staff, our mission in Kiev will be closed until further notice," foreign ministry spokesman Adam Hodge told Agence France Presse.

The White House on Wednesday called the deadly violence on the streets of the Ukrainian capital "completely outrageous" and renewed its appeal to President Viktor Yanukovych to de-escalate the situation.

Clashes in Kiev between police and anti-government protesters that have claimed 26 lives are "completely outrageous" and "have no place in the 21st century," Deputy National Security Advisor Ben Rhodes told reporters aboard Air Force One.

The French, German and Polish foreign ministers will be in Ukraine on Thursday after the deadly escalation in the country's political crisis, French Foreign Minister Laurent Fabius said.

Calling for "restoring political dialogue between the opposition and the government," Fabius said he, German Foreign Minister Frank-Walter Steinmeier and Poland's Radoslaw Sikorski would hold meetings in Ukraine early Thursday before emergency talks among EU ministers in Brussels.

Anti-government protesters were locked in a stand-off with riot police across burning barricades Wednesday after fierce clashes left at least 26 people dead in Ukraine's worst crisis since the collapse of the Soviet Union.

The crackdown by security forces triggered a storm of international condemnation, with the White House calling the violence "completely outrageous".

Riot police launched a fresh assault on protesters in central Kiev early Wednesday, escalating a bloody standoff that has already left at least 16 people dead in a dramatic turning point for Ukraine's three-month political crisis.

A volley of tear gas rained down on protesters and more tents went up in flames as riot squads took up position around a monument in the center of Independence Square shortly after 4:00am (02:00 GMT).

EU foreign policy chief Catherine Ashton on Tuesday denounced the "grave new escalation" in Kiev, where at least five people were killed and scores hurt as protestors battled police.

"I am deeply worried about the grave new escalation in Kiev and the reported victims," Ashton said in a statement, saying she condemned "all use of violence, including against public or party buildings."

Protesters hurled Molotov cocktails as Ukrainian riot police firing stun grenades and water cannon stormed the main anti-government protest camp Tuesday, after the bloodiest day of protests left at least eight people dead and triggered international alarm.

Police broke through barricades with armored vehicles, but faced thousands of protesters armed with stones, fireworks and petrol bombs who had refused to obey an ultimatum to evacuate Kiev's iconic Independence Square.

Russia on Tuesday blamed the policies of Western countries for the latest clashes between pro-EU protesters and police on the streets of Kiev.

"What is happening is a direct consequence of the policy of connivance among those Western politicians and European agencies that have been shutting their eyes to the aggressive actions of Ukraine's radical forces since the beginning of the crisis," the Russian foreign ministry said in a statement.

Ukrainian opposition protesters on Tuesday attacked the party headquarters of embattled President Viktor Yanukovych as fierce clashes with police erupted again in Kiev for the first time in weeks.

Protesters briefly seized the party headquarters after several hundred attacked it with Molotov cocktails and smashed their way inside but later withdrew as smoke continued to billow from part of the building, an Agence France Presse reporter at the scene said.

Seven miners were killed and nine injured when a gas explosion ripped through a state-owned coal mine in eastern Ukraine, officials said Tuesday.

The blast occurred Monday evening at a depth of around 800 meters (2,600 feet) while some 90 workers were on shift at the mine in Makiyivka in Ukraine's mineral-rich Donetsk region.