Two rockets have struck a runway at the international airport in Libya's capital Tripoli, forcing the suspension of flights, an airport source said.

"Two rockets exploded on the main runway of the airport, causing damage. For security reasons, flights were suspended until further notice," the source said on Friday on condition of anonymity.

The blasts took place at around 5am local time (0300 GMT), at a time when the day's inbound and outbound traffic had yet to begin.

An airline representative in the capital said that the authorities had informed firms operating at the airport that flights would remain suspended until 1030 GMT on Saturday, according to AFP news agency.

Since long-time dictator Muammar Gaddafi was deposed in 2011 and killed by rebels in October that year, the international airport has been under the control of former opposition fighters from Zintan, 170 km southwest of Tripoli.

It is at Zintan that Gaddafi's son and one-time presumed heir Saif al-Islam is being held by ex-rebels.

The North African country's transitional authorities have so far failed to disarm former rebel militias or integrate them into Libya's armed forces.

Eastern Libya has become a bastion of armed groups, with authorities avoiding a full-blown confrontation with heavily armed former rebels pending the formation of a regular army and police force.

On Thursday, however, the government announced it was mobilising its security forces after stating for the first time that "terrorist groups" were behind dozens of attacks against security services and foreigners.

"The nation finds itself in a confrontation with terrorist groups, and it falls upon the government to mobilise its military and security forces to fight this scourge," said a statement published on the government's website.