Pro-government demonstrators in Libya have marched on the headquarters of the Ansar al Sharia group in the eastern city of Benghazi. The Salafist group is accused of involvement in the recent attack on the US consulate. Hundreds of protesters forced an Islamist group out of its Benghazi base on Friday evening. The AFP news agency reported that protesters set fire to the compound and quoted hospital sources as saying three people were killed in the incident. The Salafist group Ansar al Sharia was forced to vacate its headquarters a few hours after a mass rally in the city center, in which an estimated 30,000 people took to the streets to protest the group's power in Benghazi. The group has been accused of conducting the September 11 attack on the US consulate in Benghazi, in which a US diplomat and three other State Department staff members were killed, but it denies any involvement. US Secretary of State Hillary Clinton on Friday described that incident, for the first time, as a "terrorist attack," saying the US would not rest until those responsible were brought to justice. Clinton was speaking ahead of a meeting with Pakistan's foreign minister. The demonstration, called "Rescue Benghazi" or "Save Benghazi" day, demanded that the government disband militia groups in Libya that have not thrown down their arms since last year's ouster of Moammar Gadhafi. The eastern city of Benghazi was one of the military and political strongholds of the ultimately NATO-backed rebels in last year's Libyan conflict, and remains a restless Libyan city even after regime change.