A militia shelled Tripoli airport, destroying 90 percent of planes parked there, a Libyan government spokesman said, as heavy fighting between armed groups prompted the United Nations to pull its staff out of the North African country.

At least 15 people have been killed in clashes in Tripoli and the eastern city of Benghazi since Sunday, and a Libyan official said several Grad rockets hit the Tripoli International Airport on Monday, damaging the control tower.

Government spokesman Ahmed Lamine said 90 percent of the planes parked at the airport were destroyed.

"The government has studied the possibility to bring international forces to enhance security," he told reporters On Tuesday.

Three years after the fall of Muammar Gaddafi, Libya has slipped deeper into chaos with its weak government and new army unable to control brigades of former rebel fighters and militias who often battle for political and economic power.

Two soldiers were killed and a number of planes were damaged when a militia shelled Tripoli airport on Monday, a Libyan soldier told Reuters.

"Several planes and cars belonging to citizens were hit," said Abdel Rahman, a soldier in a unit protecting the airport. A hall used by customs controls had also been hit, he added.

Seven people were killed in Tripoli on Sunday in the worst fighting for six months in the capital, where rival militias have been fighting for control of the airport.

Security and medical sources said at least six people had been killed and 25 wounded in Benghazi in heavy fighting between security forces and rival militias since late Sunday.

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