Ukraine's Prime Minister Mykola Azarov warned on Tuesday that the security forces could use force to disperse protests after two nights of clashes that left hundreds wounded.

Azarov told Russian television that if "provocateurs" did not stop, the authorities could act under controversial new laws that essentially ban large protests in Ukraine.

His comments came as influential news site Dzerkalo Tyzhnia said that the authorities had already worked out a precise plan to regain control of the site of the intense clashes between protesters and the security forces.

Russian Foreign Minister Sergei Lavrov warned the situation in Ukraine was spiralling out of control after two months of protests over President Viktor Yanukovych's failure to sign a deal with the European Union.

Clashes raged in the centre of the Ukrainian capital until early morning Tuesday, with demonstrators flinging Molotov cocktails and stones at security forces who hit back with stun grenades, rubber bullets and tear gas.

The day was relatively calm but sporadic clashes resumed late in the night Tuesday, an AFP correspondent said. However the exchanges lacked the ferocity of previous evenings.

"If the provocateurs do not stop then the authorities will have no choice other than to use the force set out under the law and ensure the security of our people," Azarov told Russia's Vesti 24 state news channel in an interview.

A new set of laws, which ban nearly all forms of protest in the ex-Soviet country and have enraged demonstrators, were officially published in the newspaper of the Ukranian parliament.

They allow for jail terms of up to five years for those who blockade public buildings and the arrest of protesters wearing masks or helmets.

Azarov added that he hoped there would be no need for the use of force to disperse the protests.

"We are hoping for common sense," he added. "People need to understand that they are being offered chaos and destruction."

Russia warns 'situation out of control'

Russian Foreign Minister Sergei Lavrov said the fact that calls by Ukraine's pro-EU opposition leaders to refrain from violence failed to calm tensions in the capital meant that the situation was becoming explosive.

"They show that the situation is getting out of control," said Russia's top diplomat.

Lavrov described the violent protests as "scary" and an "absolute violation of all European norms of behaviour".

He also slammed the EU's "indecent" support of the protest movement against Yanukovych.

On Tuesday, the UN's High Commissioner for Human Rights, Navi Pillay called the situation in Ukraine "very worrying" and said the government should suspend the controversial anti-protest laws.

Clashes on Sunday and Monday, which followed two months of protests, turned an area in the centre of the capital Kiev into a veritable war zone as some 10,000 demonstrators battled security forces.

Demonstrators rigged up a giant catapult behind a barricade of burned out police buses in order to better hurl projectiles at the security forces. However this appeared to have been destroyed in the clashes early Tuesday.

Dzerkalo Tyzhnia said the planned assault on the protest zone would involve 8,000 members of the security forces but its timing had yet to be made clear.

It said that authorities had also yet to determine whether to disperse protesters at just the site of the violent clashes or the main protest hub of Independence Square as well.

Prominent activist 'kidnapped'

Police said 163 members of the security forces were wounded and 80 of them were hospitalised. Activists said hundreds of protesters were hurt but the precise number was not clear.

At least 35 journalists were hurt in the clashes and some received injuries to their faces and eyes from rubber bullets, Ukrainian press freedom group the Institute of Mass Information said.

The interior ministry said 50 activists had been arrested as part of an investigation for mass rioting.

Meanwhile a prominent Ukrainian activist and journalist, Igor Lutsenko, on Tuesday said he was safe and well after being abducted from a hospital by unknown individuals and dumped in a forest outside Kiev.

He wrote on his Facebook page after being released that he had indeed been abducted from a hospital in Kiev and was eventually left in a forest by his abductors after an ordeal lasting almost a day.

Protesters at the scene of the clashes also said that they had received mysterious text messages warning them that "dear subscriber, you have been registered as a participant in mass disorders."

The opposition led by three politicians including former world boxing champion Vitali Klitschko said it was ready for dialogue but stressed it wanted to hold talks with Yanukovych, not his aides.

The opposition leaders appeared unable to have any influence on the hard core of radical protesters and stopped short of supporting their actions.