The campaign headquarters of Egyptian presidential candidate Ahmed Shafiq has been attacked by protesters.
Egyptian TV stations broadcast footage of a fire at the building, in the Dokki district of the capital Cairo.
There are currently no reports of injuries, and the fire was quickly put out with no signs of serious damage.
The attack comes amid protests against election results hours after it was announced that Mr Shafiq would compete in a run-off next month.
The attackers also took a number of campaign posters and allegedly took a number of computers from the building, the BBC's Jon Leyne reports from Mr Shafiq's HQ in Cairo.
Anti-Shafiq protesters then dispersed and a number of Mr Shafiq's supporters then arrived at the scene, our correspondent adds.
Crowds were also heading to the city's central Tahrir Square, scene of the protests which forced the resignation of President Hosni Mubarak in February 2011 and frequent demonstrations ever since.
More than 1,000 people have gathered in the roundabout at the centre of the square, protesting against the official election results.
Earlier on Monday, Egypt's election commission confirmed that the Muslim Brotherhood's Mohammed Morsi and Mr Shafiq will contest a presidential run-off in June.
Mr Morsi gained 24.3% of the vote in the first round of the poll held last week while Mr Shafiq won 23.3%.
However, many activists have been protesting against Mr Shafiq's candidacy as he was the last prime minister to serve under Mr Mubarak and is viewed as a representative of the old regime.