Libyan officials and witnesses say gunmen in pick-up trucks have surrounded Libya's Justice Ministry to make demands on the government.
The Foreign Ministry has been blockaded by gunmen since April 28.
The armed groups are calling for a law to be passed banning former officials of deposed leader Muammar Qaddafi from senior government posts.
Walid Ben Rabha, head of the ministry's information department, said that the armed men were in vehicles fitted with antiaircraft guns.
Other state buildings have also been targeted.
The unrest prompted the General National Congress to postpone its planned April 30 session until May 5.
A spokesman said this would give them time to study the legislation the protesters are calling for.
If passed, such legislation could force out several long-serving ministers and congress members.
Based on reporting by Reuters and dpa