A militia of Libyan ex-rebels seized control of Tripoli International airport on Monday, surrounding aircraft with tanks and grounding all flights after their leader's apparent arrest, officials said.

"It is total confusion. Everyone is fleeing. Several armoured vehicles and tanks are positioned on the tarmac, blocking traffic," an official at the airport told AFP.

"Cars mounted with anti-aircraft guns and armed men are surrounding the aircraft and preventing them from moving," another official said, adding that some passengers were forced to leave planes.

The official Lana news agency, citing witnesses, confirmed the "assault," saying that the motive of the gunmen was to pressure the government to explain the whereabouts of their leader, Abu Ajila Al-Habshi.

The agency said the gunmen fired into the air, slightly wounding an airport employee and causing panic among travellers.

Mohammed Al-Harizi, spokesman for Libya's interim government, said earlier that an investigation had been launched to determine the circumstances of the Al-Awfya brigade commander.

Tripoli's security commission, which answers to the interior ministry, said it had nothing to do with "the disappearance and abduction of Colonel Abu Ajila Al-Habshi" and that it was still tracking those responsible.

The ruling National Transitional Council (NTC) is still struggling to fully integrate many Libyans who fought forces loyal to dictator Muammar Gaddafi, who was ousted and killed in October last year.

The former rebel fighters have remained in organised armed brigades, taking upon themselves to ensure law and order in the absence of fully functional police and armed forces.

The NTC took control of Tripoli airport in April from a coalition of Zintan brigades that had been guarding the facility since the capital's liberation in August 2011.

The militias secured many strategic sites in Libya after they defeated Gaddafi loyalists backed by NATO-led air strikes during last year's Arab Spring-inspired revolution.

The NTC has called for their handover, but several other similar militias of former rebels are still guarding important buildings and facilities in the North African country.

Monday's incident at Tripoli airport comes as Libya prepares to hold elections for a 200-seat constituent assembly by 19 June, as pledged by the NTC.

Flashes of violence, such as a deadly raid on government headquarters last month, have raised concerns over the capacity of authorities to secure the first election after decades under Gaddafi.

Ethnic unrest in the south, calls for greater autonomy in the east and corruption are some of the challenges facing Libya's interim leaders.

Since the start of the Arab Spring, elections in the region have benefited Islamists, including in Egypt, Libya's neighbour to the east, and Tunisia to the west.