Hundreds of Islamists rallied outside the Interior Ministry in Tunis after Friday prayers and marched on Abdallah Guech Street, a center of officially tolerated prostitution, Mourad Barhoumi told The Daily Telegraph.
"There were several dozen riot police who shut off entry to the neighborhood," he said. "They fired in the air to break up the crowd, which didn't want to go until the brothel was shut."
At least three people were reported wounded.
The demonstrators dispersed after a military official announced the brothel had been closed down. It was the third one shut by the movement in recent weeks.
Islamists have been organizing in Tunisia since the overthrow of dictator Zine al-Abidine Ben Ali, who suppressed their movement.
Elections to replace him are expected in the summer, and at least one Islamist candidate is expected to run.