Ukrainian police have started a crackdown on pro-EU protesters in downtown Kiev, dismantling protest tent camps in front of government buildings.

Police were seen forcing protesters out of two streets where, according to the Interior Ministry, they were blocking access to administrative buildings.

Oleg Tyagnibok, leader of the nationalist formation Freedom, has reported that at least ten protesters have sustained injuries during the removal of barricades near the headquarters of the presidential administration.

According to him, riot police have managed to push the protesters away. He pledged this was just temporary.

"We will return tomorrow. The stronger force they use, the stronger the resistance of the people," Tyagnibok has said, cited by the Russian news agency Interfax.

Policemen have also been injured during the dismantling of barricades. Local media report that one officer of Berkut, Ukraine's special police unit, has been sprayed with teargas by a demonstrator. A soldier has been hurt in the melee. He is in the hospital, but his diagnose is pending.

The opposition Fatherland party of jailed former Ukrainian Prime Minister, Yulia Tymoshenko, said security forces had raided its headquarters. However, a police spokeswoman insisted later that neither the regular Kiev police nor Berkut riot police had conducted any operations at the address.

It was reported meanwhile that US Vice President, Joe Biden, has spoken over the phone to Ukrainian President Viktor Yanukovych, expressing "deep concern" about the situation in Kiev and urged dialogue with the opposition.

"[Mr Biden] noted that violence has no place in a democratic society and is incompatible with our strategic relationship," the White House said in a statement.

Hundreds of thousands of people have been protesting in Kiev's Independence Square against the recent decision of Yanukovych and his government to back out of a strategic deal with the EU and seek closer ties with Russia.