Islamist-led militiamen stepped up their assault Sunday on Libya's main airport, two days after the collapse of a truce with rival ex-rebels who control the facility, a security official said.
The renewed fighting, which killed at least five civilians, was condemned by the European Union, which urged restraint and dialogue.
A coalition of militias led by Islamist fighters launched an assault on Tripoli international airport, with clashes later spreading to the road leading to the capital.
"The airport was attacked this morning with mortar rounds, rockets and tank fire," airport security official Al-Jilani al-Dahesh told AFP.
"It was the most intense bombardment so far," since a week-old battle for control of the airport erupted on July 13.
Dahesh said the militia which controls the airport, based in Zintan, southwest of the capital, and seen by Islamists as the armed wing of liberals within the government, responded with heavy fire.
Islamist militias have been joined by other armed groups, including the powerful Misrata Brigades which played a key role in the 2011 UN-backed revolt that toppled and killed strongman Moamer Kadhafi.
The fighting has forced a halt to all flights and caused extensive damage to planes and airport infrastructure, with aviation officials saying Tripoli airport could stay closed for months.
Pictures posted on social media showed a Libyan Airlines plane on fire as plumes of smoke billowed over the airport.
The carrier said on its Facebook page that one of its aircraft, a Bombardier CRJ900, was destroyed.
By midday on Sunday, fighting had spread to other sites on the airport road that are controlled by the Zintan militia, an AFP correspondent said.
Loud explosions were heard in the city centre, 25 kilometres (15.5 miles) away, as battles raged along the airport road with rockets striking nearby homes.
At least five civilians were killed in the Qasr Bin Ghashir neighbourhood, Mohamed Abderrahman from the local town council, told private Al-Nabaa television.
The rival sides are among several heavily-armed militias which have held sway in the oil-producing North African nation for the past three years.
- 'No military solution' -
Relentless violence across Libya this year -- including a war against Islamists in the east launched by a rogue general -- has sparked fears of all-out civil war.
The European Union mission in Libya issued a statement Sunday urging fighters to lay down their arms and spare civilian lives.
"The EU is concerned about the protracted conflict over Tripoli international airport and urges all parties to exercise restraint, to abide by international law and to respect civilians," it said.
"The EU calls on all parties to find a peaceful resolution through dialogue and compromise... there is no military solution to the crisis in Libya ... the only option is a political solution and a peaceful democratic process."
On Thursday, Foreign Minister Mohamed Abdelaziz pleaded for UN help to build up Libya's army and police force and to protect vital sites, including the airport and oil installations.
The fighting mirrors a deadly power struggle between liberals and Islamists in the National General Congress, Libya's parliament and top political authority.
A new parliament was elected last month after the GNC came under repeated accusations of trying to monopolise power.
Results of the vote had been due to be announced Sunday but the electoral commission announced a delay until Monday.