Smoke shrouded the headquarters of the National Oil Corporation (NOC) in Tripoli [Hani Amara/Reuters]

Armed men have stormed the headquarters of Libya‘s National Oil Corporation (NOC) in Tripoli, where a blast and gunfire were heard, according to witnesses.

The building in the Libyan capital’s centre caught fire on Monday, witnesses said, and security forces are smashing windows so staff could escape.

“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, an armed goup that operates as Tripoli’s police force.

“The situation is under control,” he told AFP news agency.

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

An NOC staff who said he jumped out of a window to flee told Reuters there were three or four gunmen inside the building.

“Several people were shot,” he said.

No group has so far claimed the attack.

Photos posted on social media showed wounded people being carried from the scene as firefighters tried to evacuate people from the building’s top floors.

A member of staff from a hotel next to the NOC offices told Reuters he had heard about five blasts.

Al Jazeera’s Mahmoud Abdelwahed, reporting from Tripoli, said the situation was still uncertain.

“Special security forces have cordoned off the area surrounding the headquarters of NOC and are engaging with the gunmen,” he said.

“We are also getting reports some employees trapped inside are calling for help and that people living nearby are trying to help them escape from other gates,” he added.

Musthafa Sanallah, NOC chairman, was safely evacuated from the firm, Reuters said.

Libya’s chaos explained: ‘Everybody vying for a piece of the pie’

Tripoli was shaken by clashes between rival armed groups at the beginning of this month but the capital has also seen occasional attacks.

Tripoli was shaken by clashes between rival armed groups at the beginning of this month but the capital has also seen occasional attacks.

In May, fighters affiliated with the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group claimed a deadly attack on the national election commission offices in Tripoli.

The group had also claimed an attack in 2015 on the Corinthia hotel, a landmark location in Tripoli.

Ambulances and security vehicles near the headquarters of the National Oil Corporation (NOC) in the Libyan capital [Hani Amara/Reuters]