Armed men stormed the headquarters of Libya's National Oil Company in Tripoli, engaging guards in a deadly gun battle with at least one large blast going off in an apparent suicide attack.
At least two of the company's staff were killed and 10 wounded, the health ministry said. Two gunmen also died in the attack on Monday when security forces fought to regain control of the key building in the centre of the Libyan capital.
"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 the Deterrence Force, a militia that operates as Tripoli's police force.
"The situation is under control," he added.
'Number of hostages'
According to the interior ministry, the bodies of at least two attackers were found inside the NOC's headquarters.
"A total of six perpetrators appear to have attacked the building where they took a number of hostages," Interior Minister Abdulsalam Ashour was quoted as saying by Al-Ahrar television channel.
The Deterrence Force described the incident as a "terrorist" attack and posted photos on its Facebook page that it said showed remains of suicide bombers.
An explosion rocked the building soon after the attackers went in, starting a fire that swiftly spread through the lower floors.
No group claimed the attack so far. But the interior ministry said in a statement initial indications showed the gunmen were affiliated with Daesh and the Levant.
It was the first attack of its kind against the top managers of Libya's state oil industry. Armed groups regularly block oilfields to make demands, but the NOC headquarters had so far been spared the violence.
Security forces smashed windows so staff could escape and several people were hurt by shattered glass.
"The building was heavily damaged due to the fire. Smoke is everywhere," the head of the company, Mustafa Sanallah, told a Libyan television channel.
"The gunmen attacked the lower floors with random shooting and explosions. It's a very violent attack."
Sanallah confirmed to the Libya 218 news channel that staff members had been killed and others wounded, some of whom were in "serious condition".
An NOC staff member, who said he jumped out of a window to flee, told the Reuters news agency on condition of anonymity "several people were shot" during the attack.