Opposition protesters were Monday locked in a tense standoff with Ukrainian police in Kiev after bloody clashes that wounded over 200 people, as President Viktor Yanukovych called emergency talks to resolve the crisis.

The clashes, the worst in Kiev in recent times, came amid mounting anger over laws restricting protests signed by Yanukovych after almost two months of demonstrations against his refusal to sign a pact for integration with the EU.

A special commission set up by Yanukovych was due to meet representatives of the opposition on Monday for emergency talks, but it was unclear if this could help ease the crisis, with parts of central Kiev resembling a battlefield.

In near apocalyptic scenes close to parliament and the iconic Dynamo Kiev football stadium, protesters torched several police buses and vehicles late Sunday.

Police responded with tear gas, stun grenades, rubber bullets and water cannon.

After a night of violence that continued into the early hours, thousands of protesters came to the streets Monday morning despite temperatures of minus 10 degrees Celsius.

The situation remained tense with protesters launching occasional charges against the police line guarding the passage to government buildings, throwing stones or Molotov cocktails.

"We are going to stay here until our demands are met on the annulment of the laws" restricting protests, said protester Yaroslav Pyutilin, 46.

According to the Kiev health authorities, more than 100 protesters were wounded in the clashes, with four people sustaining serious injuries to eyes and limbs.

The interior ministry said more than 100 members of the security forces had been wounded.

The burned-out wrecks of the police buses were now used by the protesters as a barricade beyond which there were hundreds of riot police wearing helmets and carrying shields.

Protesters equipped themselves with ad hoc shields made of metal sheeting and wooden sticks in anticipation of further clashes with police.

The area echoed with the thud of stun grenades and the deafening drumming of groups of mostly elderly protesters with sticks on metal.

The ministry added that 20 people had been arrested for mass rioting. US-funded Ukrainian radio station Radio Svoboda said two of its journalists had been arrested Monday morning while filming at the scene.

US urges calm, threatens sanctions

The White House urged an end to the violence, with US National Security Council spokeswoman Caitlin Hayden saying that Washington was deeply concerned and urging "all sides to immediately de-escalate the situation".

The spokeswoman warned that Washington was still considering sanctions against Ukrainian officials, a step urged by the Ukrainian opposition. "The US will continue to consider additional steps -- including sanctions -- in response to the use of violence," Hayden said.

EU foreign ministers meeting in Brussels on Monday deplored the violence, saying the government was at fault for adopting the repressive laws.

The new laws allow for jail terms of up to five years for those who blockade public buildings and the arrest of protesters wearing masks or helmets. Other provisions ban the dissemination of "slander" on the Internet.

The laws were passed last week in a chaotic show of hands in parliament and then signed into law by Yanukovych.

The curbs on protests were "the most solid package of repressive laws that I have seen enacted by a European parliament in decades," Swedish Foreign Minister Carl Bildt said in Brussels.

Ukrainian opposition television broadcast pictures of two young men who it said were stripped naked by the security forces and then peppered with rubber bullets. Police said they were checking the claim.

Opposition leaders, including former boxing champion Vitali Klitschko and Arseniy Yatsenyuk, urged protesters to refrain from using force but their calls were ignored.

It was not clear who was behind the clashes with police, which appeared to have been a well-organised move. Ukrainian media linked the action to a hitherto little-known right-wing youth group called "Right Sector".

Special commission to meet opposition

In an apparent attempt to find a compromise, Klitschko travelled to the president's luxurious Mezhygirya residence outside Kiev to meet Yanukovych in person.

The president received Klitschko and promised Monday to create a special commission of officials set up by national security council secretary Andriy Klyuyev to solve the crisis, the boxer's party and the presidency announced.

The presidency said the new commission would meet the opposition on Monday but there was no sign of this yet taking place.

On Sunday afternoon, some 200,000 people had filled Kiev's Independence Square and surrounding streets for a new mass rally in defiance of new strict curbs on protests.

Protesters expressed frustration at the rally over the lack of a clear programme from the opposition leaders after almost two months of protests, whistling and heckling them for their perceived inability to mount a stronger challenge.

Yanukovych's arch nemesis Yulia Tymoshenko remains in jail, while the protest leadership appears riven by rivalries ahead of presidential election next year.