After weeks of escalating clashes among factions in the Libyan capital of Tripoli armed militants have stormed the headquarters of the National Oil Corporation (NOC).

Reuters reported smoke and ambulances ferrying injured away in an attack that eyewitnesses say started with five blasts and resulted in multiple people being shot. The large glass-fronted office complex is located in central Tripoli and the state-run NOC is responsible for exporting a combined 70% of the country's oil across its subsidiaries and facilities throughout the country.

Significant casualties have been reported with early reports saying at least six have killed. According to Tripoli security officials, two NOC employees are among the dead, and two of the gunmen have been reported killed by security forces. “Three or five gunmen were shooting inside the building,” an NOC staff members who fled the building told Reuters, and added, “Several people were shot.”

And reportedly Musthafa Sanallah, NOC chairman, who was present at the time of the attack and safely evacuated from the building, immediately told reporters that "the attack won't affect NOC operation".

National Oil Corporation (NOC) Headquarters. Image source: Reuters

The building caught fire during Monday's attack, and reports say local militias under the city's Government of National Accord (GNA) authority have restored security, though the situation remains uncertain.

According to Al Jazeera:

The building in the Libyan capital's centre caught fire on Monday, witnesses said, and security forces were 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.

NOC employees, some of whom jumped from low level windows as the attack was unfolding, say the attack started with an explosion and guards at the front of the facility came under gunfire.

NOC headquarters with smoke rising after the attack. Image source: Reuters

Al Jazeera's correspondent on the ground said the situation is still fluid: "Special security forces have cordoned off the area surrounding the headquarters of NOC and are engaging with the gunmen inside the building," Mahmoud Abdelwahed said from Tripoli.

He reported further, "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. NOC employees could be seen on top of the large building as smoke rose from burning levels below.

Unconfirmed reports say one of the attackers detonated a suicide vest during the assault:

#طرابلس | قوة الردع الخاصة تعلن إخلاء مقر المؤسسة الوطنية للنفط وتمكنها من السيطرة على الموقف وتنشر صور ترصد جانب من اقتحام قواتها وأشلاء لأحد المهاجمين الذين فجروا أنفسهم . pic.twitter.com/gA50l0FGDe — Mohammed Ali (@Mohammed_abdusa) September 10, 2018

Though the assailants are as yet unknown, some international reports are suggesting the coordinated attack could be the work of the Islamic State in Libya, which as recently as May attacked the national election commission offices in Tripoli, and in years past has attacked landmark hotels which are popular meeting places among officials.

🔴 SUIVI - #Libye: Attaque en cours contre le siège de la compagnie pétrolière d'État la National Oil Corporation (NOC) à #Tripoli, évacuation des blessés par les secouristes." pic.twitter.com/7cUxkWBK80 — FranceNews24 (@FranceNews24) September 10, 2018

In late August heavy inter-factional fighting within the UN-backed Government of National Accord (GNA) rocked Tripoli as street battles and mortar fire engulfed whole residential neighborhoods especially in the southern suburbs of the city.

The past four or five days have witnessed an uneasy truce; however, Monday's events mark the return of chaos which has gripped the city for the past weeks.

Rescue mission underway at the NOC Headquarters. The chairman Mustafa Sanalla is safe. A number of casualties reported. #Tripoli #Libya pic.twitter.com/OPB8n5kYP6 — Nadia Ramadan (@NadiaR_LY) September 10, 2018

Post-Gaddafi Libya has been largely forgotten about in the media after its "liberation" by NATO and Islamist militants, and since 2011 has existed in varying degrees of anarchy and chaos. Libya has remained split between rival parliaments and governments in the east and west, with militias and tribes lining up behind each, resulting in fierce periodic clashes.

Perhaps the most significant of these warring militias nationwide is Khalifa Haftar's Libyan National Army, which controls much of eastern Libya and is the chief rival to the GNA in the western half of the country.

Haftar has reportedly been planning to make a move on Libya's vital "oil crescent region" while bolstering his forces with Chadian mercenaries, according to local reports.

However, despite all of the political turmoil, and even sporadic attacks on oil facilities and blockades, Libyan oil production has remained somewhat stable by comparison throughout, per Reuters:

However, the NOC has continued to function relatively normally across Libya, which relies on oil exports for most of its income. Oil production has been hit by attacks on oil facilities and blockades, though last year it partially recovered to around one million barrels per day (bpd).

But it's entirely possible after today's events that that is about to change.

Prior the 2011 Libyan war and NATO military intervention which ultimately led to the field execution of Muammar Gaddafi, the country produced about 1.6 million bpd, but years of turmoil and political instability in the aftermath have slashed that to 550,000 barrels per day as of June.