About 500 people broke into the grounds of Libya's parliament building on Sunday to demand an end to fighting in Bani Walid, a former stronghold of the late Muammar Gaddafi.
Most of the protesters were residents of Tripoli with family connections to Bani Walid.
Elected members of the General National Congress were meeting inside at the time.
Militia forces from Misrata, aligned with the Defence Ministry, have been shelling the town of 70,000 people 140km south of Tripoli for several days.
The LANA news agency said 22 people have been killed and 200 wounded in the fighting there.
Another group of protesters broke into the assembly grounds on 4 October.