Armed men assaulted the headquarters of a Libyan militia in Tripoli and torched it Friday, hours after shooters inside fired on demonstrators who were calling on them to leave the city, witnesses said. They entered the district of Gharghour where the  headquarters is located "and set fire to all the villas (the militia) occupied so that they would not return," said one witness, who identified himself only as Ibrahim. "Most of the members of the militia barricaded themselves inside one single villa, but the noose is tightening around them," he added.