WASHINGTON - The US government stepped up pressure on Ukrainian President Viktor Yanukovych on Thursday amid the newly-erupted violence in Kiev, warning of sanctions.

In a phone call, US Vice President Joe Biden urged Yanukovych "to take immediate and tangible steps to work with the opposition on a path forward that addresses the legitimate aspirations of the Ukrainian people," according to a statement issued by Biden's office.

He "strongly condemned" the violence against civilians in Kiev and demanded for immediate withdrawal of security forces, it said.

Biden said the United States is prepared to sanction those officials responsible for the violence."

Earlier in the day, the White House has prodded Yanukovych to "immediately withdraw" his security forces from downtown Kiev and resolve the conflict by political means.

It also urged the Ukrainian military "not to get involved in a conflict that can and should be resolved by political means," warning that the US would work with its European allies to hold those responsible for violence accountable.

After the latest violence in Ukraine, foreign ministers of the European Union (EU) agreed Thursday to adopt sanctions against the country, including asset freezes, visa bans and ban on exporting anti-riot equipments.

The West's sanctions and threats were rejected by Russian Foreign Minister Sergei Lavrov, who desribed them as "blackmail and double standards."

"The opposition cannot or do not want to distance itself from extremists. The West led by Europe and the United States assume all responsibility for Ukraine situation," he said on Thursday.

At least 67 people have been killed in the past three days of violence in central Kiev, the Kiev City Administration said Thursday. It also said that 551 people were injured and 332 of them hospitalized since Tuesday.

Protests in Kiev began in November after Yanukovych backtracked on a trade deal with the EU and tilted toward Russia instead. They turned violent in mid-January and have been remarkably escalating this week.