Ukrainian police on Wednesday broke through the barricades built by protesters at the scene of clashes in Kiev as activists said that one person had been shot dead by the security forces.
In chaotic scenes, police stormed the protesters' barricades shortly after 0600 GMT on Grushevsky Street in Kiev, an AFP correspondent said.
New clashes broke out as the police arrested protesters and created a large hole in the barricades which the protesters had based on the burned out wrecks of destroyed police buses.
Police threw stun grenades into the area where the protesters were standing as protesters responded by throwing stones.
Meanwhile the medical service of the Ukraine protest movement in Kiev said one male protester had died from wounds sustained after being shot by a police sniper.
The interior ministry confirmed the death but said it was not clear what had caused it, the Interfax news agency said.
The medical centre for protesters also said another activist died after falling from the top of the ceremonial entrance to the Dynamo Kiev football stadium adjacent to the clashes. This has not been confirmed by the interior ministry.
The police, protected with helmets and riot shields, advanced some 50 metres (160 feet) towards the Dnipro Hotel which lies at the end of Grushevsky Street.
However the police then retreated back to their former positions, although it was not clear if this was just to regroup before launching a new assault.
The police warned protesters not to approach closer than three metres (10 feet) to their lines, saying this would be considered a threat against the life of a policeman.
There was so far no move by the police against the main protest camp on Independence Square.
Ukraine's Prime Minister Mykola Azarov had warned on Tuesday that the security forces could use force to disperse protests. Three nights of clashes have 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 using 8,000 members of the security forces.
Russian Foreign Minister Sergei Lavrov warned on Tuesday that 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.
"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.
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," Russia's top diplomat said.
Lavrov described the violent protests as "scary" and an "absolute violation of all European norms of behaviour".
Police said Tuesday evening 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.
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 taken 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.