Budapest - Anti-government protesters clashed with Hungarian police yesterday as political tension erupted into violence on the anniversary of the bloody 1956 revolution.

Police fired rubber bullets, teargas and water cannon to disperse hundreds of demonstrators, some of whom hurled stones and waved nationalist flags, as they marched towards the parliament where dozens of dignitaries were commemorating the uprising.

Thousands of police flooded central Budapest to quell the riots, as Hungarians marked 50 years since the crushing of their demand for an end to Russian domination. A T-34 tank - like those used by the Soviet army to crush the 1956 uprising - was taken by protesters from a nearby exhibit and driven towards the police lines. "The whole crowd started cheering. The police started firing teargas, then the tank stopped," a Reuters cameraman said. Police then rushed the tank, pulling out at least one person.

A second tank was also stolen and pushed by the rioters towards the police.

Helicopters hovered over the capital, ready for more trouble after last month when in two nights of rioting tens of thousands rallied to demand the resignation of the Socialist prime minister, Ferenc Gyurcsany. In the early hours of yesterday, police had cleared protesters away from the parliament before more than 15 heads of state and scores of ambassadors gathered to lay white roses at a monument to the 1956 uprising.

Mr Gyurcsany laid his rose next to that of President Laszlo Solyom, who had urged the parliament to consider ousting the Socialist leader after he admitted that he had lied about the dire state of the economy to win re-election. His admission sparked the worst protests since 1956.

Welcoming the foreign delegations, Mr Solyom urged Hungarians to unite around the memory of 1956. "People are not only celebrating separately, they are also celebrating different things," the president complained at a gala concert on Sunday night. "The fashionable slogan is that there were many 1956s, but I say there is only one 1956 revolution!"

His appeal went unheard yesterday, however, as the opposition party Fidesz boycotted state-backed ceremonies and held a huge rally of its own, addressed by rightwing politicians who invoked 1956 in calling for Mr Gyurcsany's resignation. At least 2,500 people died in the 1956 fighting, and 200,000 more fled to the west.

As the Fidesz leader, Viktor Orban, took the stage, police units around the city were isolating and arresting groups of rioters and striving to keep main roads open to allow the visiting heads of state to move around Budapest and make their way back to the airport.

Fidesz distanced itself from last month's rioting, which injured more than 200 people, but it has maintained pressure on Mr Gyurcsany to step down.

The Socialist leader has insisted he will not give in to street protests and vowed to push through the unpopular tax rises and cutbacks needed to slash the biggest budget deficit in the EU - but which he advocated only after being re-elected. "Despite often justified disappointment and discontent, most Hungarians believe parliamentary democracy is best suited to expressing the people's will and to creating law and giving a programme to a free Hungary," he said.

Several veterans of 1956 refused to shake his hand when they received awards Sunday night, and many attended a third set of events yesterday to show their disgust for the elite. "Heads of state should have boycotted those events," said Elemer Bogyay, who fled after the revolution and returned from Canada for its 50th anniversary. "After Gyurcsany lied and admitted to it, I wouldn't be able to shake hands with him - it's really a disgrace."