Crisis talks in Kyiv

US Vice President Joe Biden warned Ukrainian President Viktor Yanukovych during a phone call that Washington would not hesitate to impose sanctions against government officials responsible for violence against civilian protesters.

"He called upon President Yanukovych to immediately pull back all security forces - police, snipers, military and paramilitary units, and irregular forces," the White House said in a press release.

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

Prior to Biden's warning, the Obama administration had already put 20 Ukrainian officials on a visa blacklist. Additional sanctions would likely include asset freezes.

The White House said it was considering a range of punitive measures, and US lawmakers were reportedly drafting legislation to back up a move by President Obama to impose sanctions.

Biden's warning came hours after EU foreign ministers had already agreed in Brussels on Thursday to impose travel bans and asset freezes against some Ukrainian officials.

Talks through the night

The foreign ministers of Germany, France and Poland negotiated with President Yanukovych and Ukraine's opposition through the night until dawn on Friday in a bid to end the lethal clashes between protesters and security forces. The EU supports a political roadmap that includes an interim government and early elections.

Polish Foreign Minister Radoslaw Sirkorski said the talks ran until 0720 a.m., Kyiv time. A European diplomatic source quoted by Reuters said: "There is a break now. The participants will come back together again before midday."

The source added: "The negotiations are very difficult."

On Friday morning, several thousand protestors milled around Independence Square, known as Maidan. Police forces were not visible on the square.

Worst violence since Soviet era

The tense standoff between protesters on Kyiv's Independence Square and government security forces boiled over on Thursday into the deadliest violence in Ukraine since the collapse of the Soviet Union. Uniformed snipers fired on protesters, while some media outlets reported that elements of the opposition were also armed.

According to Ukraine's Health Ministry, at least 75 people have been killed since Tuesday. But Dr. Oleh Musiy, the medical coordinator for the protesters, told the Associated Press that at least 70 protesters were killed in Kyiv on Thursday alone, while over 500 had been wounded in the clashes.

Video footage on Ukrainian television showed protesters cut down by sniper fire. Meanwhile, the Ukrainian Interior Ministry has accused protesters of taking 67 police officers hostage.

In an effort to end further bloodshed, Ukraine's parliament passed a measure late on Thursday that would prohibit the "anti-terrorist operation" threatened by President Yanukovych. It was unclear, however, whether or not the prohibition would hold.

According to the Interfax news agency, presidential advisor Marina Stavnichuk had said that the measure would go into effect immediately. But she added that the president and Interior Ministry would have to develop a way to implement it.

slk/crh,ipj (AP, AFP, dpa, Reuters)