At least two staff members have been killed after an armed group stormed and attacked the Tripoli headquarters of the National Oil Corporation (NOC) in Libya on Monday afternoon.
Security forces clashed with the armed men at the landmark building in the centre of the city, and blasts and gunfire could be heard, witnesses have told BBC.
A security official at the site said at least two staff members and two gunmen have been killed in the attack.
Last week, the UN announced that a truce between warring militias had been agreed in the capital.
A UN-backed government is nominally in power in Tripoli but militias occupy much of the rest of the country.
A member of staff, who said he had jumped out of a window to flee, told Reuters news agency three or five gunmen were shooting inside the building and several people had been shot.
The NOC chairman, Mustafa Sanallah, has been safely evacuated, a witness quoted by Reuters added.
Rescue services are at the scene to treat the wounded coming out of the building.
“The death toll so far is two killed from NOC staff and two attackers,” said Ahmad Ben Salim, spokesman for the Special Deterrence Force (Rada) force, according to Reuters.
It is not yet clear who carried out the attack.