Hungarian police fired tear gas to disperse a crowd of protestors 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 on Saturday 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 protestors, 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 protestors, 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 organized 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, protestors 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.
Last year's 1848 commemorations were marred when police clashed with around 1,000 protestors demanding the release of a right-wing leader who had been arrested for his involvement in previous riots.
Trouble first broke out in Hungary in September 2006 following the leak of a tape on which Gyurcsany admitted lying about the state of the economy.
Rioting continued sporadically during the following month, and a Fidesz rally October 23, marking the 50th anniversary of Hungary's failed 1956 uprising against Soviet rule, ended in chaos as violent protestors and riot police mixed in with people leaving the event.