KIEV (AFP) - The police and protesters clashed in the centre of the Ukrainian capital Kiev on Sunday after 200,000 massed for an opposition rally in a show of defiance against strict new curbs on protests.

The bloody clashes left over two dozen injured and further raised tensions in the almost two-month stand-off between the opposition and President Viktor Yanukovych, which has seen protesters seize control of the centre of Kiev.

Police used tear gas, stun grenades and water cannon in a bid to disperse the hundreds of people who sought to storm police cordons near the Verkhovna Rada parliament in the capital, witnesses and AFP correspondents said.

Some demonstrators rocked police buses outside the Verkhovna Rada and set two of them on fire while the air filled with the stench of tear gas used against them.

The police said it was not aware of water cannon being deployed against the protesters, saying a fire-fighting truck was used to put down the bus fire.

Their faces covered by scarves or balaclavas, many of the protesters wielded sticks or even chains. They were met by helmeted riot police equipped with shields.

At least nine protesters were hurt and ambulances had a hard time getting through to the scene, an AFP correspondent reported. Police said 20 officers were hurt and 10 hospitalised.

The flames from the blazing police bus lit up the evening sky while the thud of smoke bombs and stun grenades echoed around.

In what amounted to a pitched battle, the protesters threw stones and sought to penetrate police lines whenever the tear gas and smoke cleared.

Opposition leaders including former boxing champion Vitali Klitschko and Arseniy Yatsenyuk denounced violence and called on the protesters to refrain from the use of force but their calls were ignored.

They also urged the president to call off the police.

"I call on President Yanukovych: find it in yourself not to repeat the fate of (Nicolae) Ceausescu and (Muammar) Gaddafi," said the boxer turned politician, referring to the slain Romanian and Libyan dictators.

He urged the president to "call early elections so that the situation does not get any worse".

Amid the chaos, Mr Klitschko was sprayed with powder from a fire extinguisher leaving his eyes irritated and face and clothes covered in white powder.

Earlier, some 200,000 people had filled Independence Square in central Kiev for a new mass rally against Mr Yanukovych.

But protesters expressed frustration at the main rally over the lack of a clear programme from the opposition leaders after almost two months of protests over Mr Yanukovych's decision to ditch a pact with the EU under Russian pressure.

The opposition called the rally on Independence Square after Mr Yanukovych on Friday signed off on tough new legislation banning nearly all forms of protest.

The new laws allow the authorities to jail those who blockade public buildings for up to five years and permit the arrest of protesters who wear masks or helmets.

Other provisions ban the dissemination of "slander" on the Internet and introduce the term "foreign agent" to be applied to non-governmental groups that receive foreign funding.

Many of the demonstrators at the rally wore pots and colanders on their heads while others sported ski, medical and carnival masks to mock the new legislation.

At the height of the protests last month, hundreds of thousands took to the streets calling for the President's resignation and early polls.

In a sign of the protest movement's growing impatience, the opposition leaders were jeered at during the main rally for their perceived inability to mount a stronger challenge to Mr Yanukovych.

"Unfortunately, they have not answered a question about a main leader," protester Ruslan Koshevarov said at the rally.

"There's disappointment, the politicians have not met our expectations."

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

Critics say Mr Yanukovych has followed in the footsteps of Russian President Vladimir Putin, who pushed through similar laws after returning to the Kremlin for a third term in 2012 amid huge protests against his decade-long rule.

In a sign of tensions, the President on Friday dismissed his chief of staff Sergiy Lyovochkin and will skip this week's prestigious economic forum in the Swiss ski resort of Davos.