The party of the man who officially lost the Democratic Republic of Congo's election run-off has condemned Tuesday's violence in Kinshasa.
Some 17,000 UN troops are in DR Congo to prevent violence
The Supreme Court was set on fire during protests by supporters of the losing candidate, Jean-Pierre Bemba.
His aides, however, say his party would have no reason to disrupt the court's hearing of his complaints of fraud.
President Joseph Kabila was last week declared the winner, with 58% of the vote against 42% for Mr Bemba.
The elections are supposed to draw a line under a five-year conflict in which some four million people died.
Election material damaged
The violence led the Supreme Court to suspend its hearing into Mr Bemba's claims he was cheated of victory.
Black-robed judges fled the court, as documents and furniture caught fire.
Some election material was damaged.
One of the burnt vehicles belonged to EU peacekeepers
The court has until Thursday to rule on Mr Bemba's complaints.
Fire-fighters arrived to tackle the blaze, which damaged part of the building in the capital, Kinshasa.
The BBC's Arnaud Zajtman in Kinshasa says police fired tear gas, as several hundred supporters of Mr Bemba first approached the building.
Interior Minister Denis Kalume said some of the protesters were carrying weapons and fired at the police.
Our correspondent says the police ran away and Mr Bemba's supporters then set two vehicles on fire, including one belonging to European Union peacekeepers.
UN troops fired shots in the air to disperse the protesters.
"We have sent additional troops in to secure the situation," said UN spokesman Kemal Saiki.
There are no reports of any casualties.
After the first round results were declared in August, security forces loyal to the two men clashed in Kinshasa, leaving at least 23 people dead.
The world's biggest peacekeeping force - some 17,000 men - is in DR Congo to prevent further unrest.
Election observers have said the irregularities were not on a large enough scale to overturn Mr Kabila's lead.
The results showed a regional divide, with Mr Bemba gaining most votes in the Lingala-speaking west, including Kinshasa, while Mr Kabila won by a landslide in the Swahili-speaking east.
The election was organised under the terms of a 2002 peace deal to end the conflict, which drew in the armies of nine other African countries.