Heavily armed Libyan militias have clashed in Tripoli, killing at least 20 people and forcing the capital’s only airport to close, officials said.

The health ministry said another 63 people were wounded in the fighting between two militias that are ostensibly allied with the internationally-backed government.

The gunfight underscores the lingering instability in the country seven years after a popular uprising toppled Muammar Gaddafi.

Civilians were said to be among the dead, including an airline employee who was trying to get home after Matiga airport shut down.

An airport official said staff were evacuated from Matiga airport and that five flights have been cancelled.

A picture posted on the airport’s Facebook page showed a passenger plane with its roof blown off.

The Special Deterrent Force, a militia which controls the airport, was fighting a rival militia led by local strongman Bashir al-Baqara.

Both are allied with the internationally recognised government in Tripoli. A rival government and parliament rules in Libya’s east, but across the country real power is held by an array of armed groups.

The Presidency Council — one of the three ruling bodies in Tripoli — said al-Baqara’s men wanted to release suspected al-Qaida and Islamic State members held at a prison near the airport that is also run by the Special Deterrent Force.

The government has ordered al-Baqara’s men to hand over their weapons and disband.

Special Deterrent Force spokesman Ahmed bin Salem said four of his men were killed. He said the situation is now under control, and that a number of the attackers were arrested while trying to storm the prison. On its Facebook page, the force says the prison houses 2,500 detainees.

Chaos in Libya has made it a major transit point for migrants from across Africa and the Middle East hoping to reach Europe.

On Monday, the coast guard intercepted three boats carrying at least 300 migrants bound for Europe, according to Ayoub Gassim, the spokesman for Libya’s navy. The boats departed from different points near Tripoli and the coastal city of Sabratha, he said.