Gunmen storm Libya national oil firm headquarters in Tripoli

Armed men stormed the headquarters of Libya's National Oil Company (NOC) on Monday, according to witnesses, who said a blast and gunfire were heard from the site.

The witnesses reported casualties in the attack on the building near the centre of the capital Tripoli, which they said was on fire and surrounded by security services.

There was no official confirmation of any casualties, but images have been posted online showing smoke coming from the building.

"The security services are looking for gunmen in the building, but our priority is to evacuate the civilians stuck inside," said Ahmed Ben Salem, a spokesman for al-Redaa, a militia that operates as Tripoli's police force.

"The situation is under control," he said.

He was not able to provide details on the identity of the attackers.

An oil company official, who asked not to be named, said masked gunmen had exchanged fire with guards and attacked the firm's headquarters.

"I jumped out of the window with other colleagues, and then we heard an explosion," the official said.

No group has so far claimed the attack.

Fighting in and around Tripoli since 27 August has killed at least 50 people and wounded 138 others, most of them civilians, according to the Libyan health ministry.

The violence has also forced thousands of people to escape to nearby towns or seek shelter in other districts of the capital, while many more have remained trapped inside their homes.

Libya's vital oil sector has been repeatedly disrupted by violence since a 2011 NATO-backed rebellion that toppled longtime dictator Muammar Gaddafi.

Petrochemical exports had accounted for the vast majority of state revenues under Gaddafi's rule, with production at 1.6 million barrels per day.

Since his ouster, output fell to about 20 percent of that level, before recovering to more than one million barrels per day by the end of 2017.

In May, the Islamic State group claimed a deadly attack on the national election commission offices in Tripoli.