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.

The U.N. mission in Libya said the closure of Tripoli airport and the deteriorating security situation made it impossible for it to operate.

Tripoli residents said a Grad rocket struck the airport perimeter late on Monday. A Reuters reporter at the airport heard anti-aircraft guns and other heavy weapons.

In Benghazi, irregular forces loyal to renegade former general Khalifa Haftar bombarded Islamist militia bases as part of his campaign to oust militants. Special forces clashed with militia fighters in the city.

Most of the dead and wounded were civilians, according to security and medical sources at Benghazi hospital. At least 10 houses were hit with missiles, and government offices and banks were forced to close.

Misrata city airport was also closed on Monday, and Benghazi airport has been closed since May. That leaves only two small airports in the south and a land route to Tunisia as the country's only gateways to the outside world, a flashback to the 1990s when Libya was under U.N. sanctions.

Western powers fear chaos in Libya will allow arms and militants to flow across its borders. The south of the vast desert country has become a haven for Islamist militants kicked out of Mali by French forces earlier this year.