Libyan Security forces are bracing for protest rallies in the capital, Tripoli, against the country's protracted political transition

A Libyan military spokesman said Friday that the unidentified assailants tried to enter the complex late on Thursday, but were repelled by government guards.

"The attackers ransacked cars and stole some weapons before pulling back," said Colonel Ali al-Sheikhi.

Another military source, according to an AFP report, offered a different version of events, saying that fighting broke out after a dispute among soldiers.

Tensions are growing in the war-ravaged country ahead of Friday's expected protest rallies against a decision by Libya's highest political authority to extend its interim mandate.

The General National Congress (GNC) was elected in July 2012 for a term of 18 months, but on Monday ratified a decision to extend its mandate to December 2014.

It took the decision despite the opposition of much of the population critical of its inability to halt Libya's slide into lawlessness and chaos.

When first established, the GNC's mission was to prepare for polling to form a commission tasked with drawing up a new constitution and to organize a general election.

There are growing fears that rival armed groups would engage in clashes as the political turmoil shows almost no sign of being resolved.

A "No Extension" campaign has also been launched in the eastern city of Benghazi as more protests have been called for Friday, the day the GNC's original mandate was to have expired.