Hungarian police have fired tear gas to disperse a crowd of protesters who responded with Molotov cocktails and stones following a right-wing rally as Hungary commemorated the 1848 revolution against the Austrian Habsburgs.

Trouble broke out following the rally and rock concert in downtown Budapest when Gyorgy Budahazy, one of the ringleaders of anti-government riots in September 2006, called on supporters to march on a building where Prime Minister Ferenc Gyurcsany was giving a speech.

Several hundred protesters, many of them youths wearing masks, headed in the direction of the building, reportedly beating photographers and cameramen along the way.

Riot police then confronted the protesters, facing a rain of stones and Molotov cocktails as they attempted to disperse them.

By late evening, at least 15 people had been arrested and two police officers injured.

Tensions had been raised by a referendum, held last Sunday, in which Hungarians overwhelmingly voted to cancel fees for medical treatment and higher education.

The fees were part of economic reforms aimed at cutting the budget deficit and eventually allowing Hungary to adopt the euro.

Centre-right opposition party Fidesz had billed the referendum as a judgement on an unpopular government and its economic reforms, but has refrained from repeating earlier calls for the government to resign should it lose the referendum.

An official late afternoon rally organised by Fidesz in downtown Budapest passed off peacefully, with tens of thousands heading off after listening to party leader Viktor Orban speak.

However, right-wing groups that have been involved in anti-government rioting over the last 18 months fulfilled expectations that they would use the referendum result to call for Gyurcsany to go and potentially renew street violence.

Police cordoned off parliament and also maintained a heavy presence at many of the official events commemorating the revolution.

Nonetheless, earlier in the day, protesters targeted Budapest Mayor Gabor Demszky, a member of junior coalition party the Alliance of Free Democrats, with eggs and stones as part of demonstrations against the hugely unpopular government.

The trouble was the latest flare-up in 18 months of on-off anti-government protests and violence.

© 2008 AAP