Story highlights The men are demanding the Foreign Ministry be cleansed of Gadhafi loyalists

They have anti-aircraft guns mounted on their trucks, the official says

No violence was reported in the latest in a string of armed protests

Armed men in trucks with anti-aircraft guns mounted on them surrounded the Libyan Foreign Ministry in Tripoli early Sunday and refused to allow ministry staff to enter the building, a ministry official said.

Gunmen diverted traffic away from the ministry in central Tripoli as they continued the siege through the day.

In a news conference at the scene, protesters said they had a list of demands. Their main goal was to push the General National Congress to pass a proposed law that would ban Gadhafi-era officials from holding government posts.

The political isolation law proposal has been a matter of contention among lawmakers for several months because it could push current senior officials out of office for serving under the former regime.

The protesters said they chose the foreign ministry because it employs officials who continue to serve after the 2011 revolution that overthrew Moammar Gadhafi. Another one of their demands is to "cleanse" the Foreign Ministry of former regime elements.

A foreign ministry official, who refused to be named for security reasons, said that no violence erupted during the siege, but ministry staff felt intimidated and threatened by the armed show of force.

Witnesses reported seeing more than a dozen gun trucks on roads leading to the ministry.

Watchdog groups have been calling on Libyan authorities to rein in armed groups that they say continue to pose a threat to the country's future.

"Unlawful armed groups that show up with heavy weapons and block access to government institutions demanding grievance, crosses the line of peaceful protest; it is intimidating and threatening and there should be accountability for these actions" Hanan Salah, the Libya researcher for Human Rights Watch told CNN on Sunday.

In recent months, similar incidents have taken place in the capital, with some Libyans resorting to armed protests. In some cases protesters surrounded government offices, and sessions of the country's legislature have been interrupted by armed groups who would storm their meetings.

Last month armed protesters besieged members of the General National Congress for several hours in an attempt to force them to pass the political isolation law. Gunmen later opened fire on the vehicle of the parliament speaker, who escaped unharmed.

Eighteen months after the fall of the regime, Libya remains awash in weapons and militias that the government has been struggling to control to secure the country.