Heavy fighting raged around Libya's main international airport as Islamist militia attacked liberal rivals in their Tripoli bastion. Photo: AP

Tripoli - Heavy fighting raged on Sunday around Libya's main international airport as Islamist militia attacked liberal rivals in their Tripoli bastion, in an intensifying power struggle after a controversial June election.

Exchanges of fire with heavy weapons forced the closure of the airport as foreign ministers from the North African nation's neighbours were to meet in Tunisia to consider how to aid chaos-riddled Libya.

The assault on the Zintan group by rival Islamist militants also came after the UN pulled staff from Libya citing security reasons, and as the United States warned of further escalation.

An airport official said “rockets struck inside the airport perimeter and was followed by heavy clashes between the Zintan militia which controls the airport and rival gunmen.

Loud explosions and heavy gunfire was heard in the city centre, 25km away, AFP correspondents reported.

An airport source said Zintan fighters pushed back the assailants but that clashes continued to rage around the facility, as witnesses reported seeing tanks deploy and smoke billowing in the area.

Authorities closed the airport for at least three days from Sunday after initially halting flights.

The former rebel Zintan militia helped topple strongman Mummar Gaddafi in the 2011 Nato-backed uprising, and is now well established in Tripoli, controlling the airport and military sites.

The heavily armed group, named after a hill town south-west of the capital, is considered the armed wing of the liberal movement which is jockeying for power with Islamists who dominate parliament.

Sunday's attack was claimed by the Operations Cell of Libyan Revolutionaries, a coalition of Islamist militias seen as the armed wing of Islamists within the General National Congress or parliament.

“The revolutionary forces arrive within the perimeter of Tripoli airport and clash with armed groups inside,” it said on its Facebook page.

The fighting comes weeks after the contested June 25 general election to replace the Islamist-dominated GNC, which has been mired in controversy and accused of hogging power.

Libya, awash with weapons since the 2011 uprising, has also been plagued by growing lawlessness while on the political front rival cabinets are jostling for power.

The embattled Tripoli government has been powerless to act and has struggled to establish a strong army and police force, allowing ex-rebels a free hand to act.

Sunday's clashes came just hours after the United States warned that the conflict could become “widespread” unless a new parliament is seated quickly and a new constitution drafted.

“The United States is deeply concerned by the ongoing violence in Libya and dangerous posturing that could lead to widespread conflict there,” State Department spokeswoman Jen Psaki said.

“We affirm our support for Libya's democratic transition and urge the seating of the new Council of Representatives as soon as possible.”

She insisted that drafting a new constitution “must advance without interference or violence”.

Last Sunday, Libya's electoral commission scrapped the election results from 24 polling stations, citing fraud, and said final results would be announced on July 20.

Commentators say liberals will fill most seats in the new parliament, unlike in the former assembly which was dominated by Islamists.

But the future makeup of parliament will become clear only after the formation of political blocs, since the vote was open only to “individual candidates” and lists were barred.

The mounting violence prompted the United Nations Support Mission in Libya to announce on Thursday that it was pulling out dozens of staff.

The well-armed and disciplined Zintan militia is officially under the jurisdiction of the defence ministry, and had claimed a May 18 attack on the GNC to demand its dissolution.

The group has made more enemies for itself by siding with rogue general Khalifa Haftar who has launched a deadly offensive in eastern Libya, cradle of the 2011 uprising, aimed at crushing Islamist militias. - Sapa-AFP