TRIPOLI: Pro-government forces said they captured Daesh’s (ISIS) headquarters in their main Libyan stronghold of Sirte Wednesday, scoring a major victory in a push to oust the militants from the city. Daesh fighters remained in several parts of the city, officials said, but seizing control of their headquarters has been the key goal of the forces loyal to Libya’s Government of National Accord.

The capture followed rapid gains by pro-government forces through the city Wednesday and after the United States last week launched airstrikes on Daesh positions in Sirte at the GNA’s request.

The city’s fall to Daesh in June last year raised deep concerns in the West, with fears the militants were gaining an important foothold just across the Mediterranean from Europe.

“The Ouagadougou center is in our hands,” the operations center for pro-GNA forces said, referring to the Sirte conference center where Daesh had set up base.

Reda Issa, a spokesman for the forces, said Daesh militants remained in three residential areas of the city and in a villa complex near the seafront. “The announcement of the liberation [of Sirte] will only be made once the entire city is liberated,” he told AFP.

The capture of the headquarters came after a lightning advance Wednesday that saw pro-GNA forces seize the University of Sirte campus just south of the conference center and Ibn Sina Hospital to the north.

It was not immediately clear how many fighters on either side may have been killed in the clashes, but the operations center said earlier that at least 20 militants had died in fighting for the university campus.

The operations center also said pro-GNA forces had lost contact with one of their military planes, without providing further details.

The Daesh-linked Amaq news agency said the group’s fighters had downed a warplane in Sirte, resulting in the pilot’s death.

Pro-GNA forces entered Sirte – 450 kilometers east of Tripoli – in June, after Daesh seized the city amid the chaos that followed the 2011 ouster of Moammar Gadhafi.

Their advance slowed as the militants hit back with sniper fire, suicide attacks and car bombings but Sunday pro-government forces said the “countdown” had begun for the final assault on Daesh’s holdout positions in the city.Washington launched its airstrikes on Aug. 1, with President Barack Obama saying it was “in America’s national security interest” to help the GNA “finish the job” of ousting Daesh from Sirte.

In a statement Wednesday, the U.S. Africa Command said 29 strikes had been carried out against Daesh positions as part of “Operation Odyssey Lightning” as of Tuesday.

The pro-GNA operations center said further U.S. raids were carried out Wednesday but did not say how many. The raids targeted Daesh positions, destroyed two armored vehicles and stopped an explosives-laden car before it could reach loyalist forces.

The Washington Post reported Tuesday that U.S. commandos were working from a joint operations center on the outskirts of Sirte, the first time they have directly supported Libyan forces in the anti-Daesh fight.

Quoting U.S. officials speaking on condition of anonymity, the Post said the U.S. forces were operating alongside British troops, helping to coordinate American airstrikes and providing intelligence.

The Pentagon would not comment on the specifics of the Post story, but has previously acknowledged small U.S. teams are in Libya.

GNA chief Fayez al-Sarraj had told Italy’s Corriere della Sera in an interview published Wednesday that his government had asked only for “airstrikes which must be very precise and limited in time and geographical scope.”

“We do not need foreign troops on Libyan soil,” Sarraj said.

Western powers are backing the GNA in a bid to bring stability to Libya, which has been wracked by turmoil since Gadhafi was ousted and killed in October 2011, with rival governments vying for power and armed groups battling to control vast energy resources.

As well as fears over Daesh, Western nations are also deeply concerned over the fate of Libya’s vast oil reserves, the largest in Africa. Six Western countries including Britain, the United States and France called Wednesday for control of all oil facilities in Libya to “be transferred unconditionally and without preconditions or delay” to the GNA.

The countries expressed particular concern about “reports of increasing tension” near Zueitina, one of Libya’s largest coastal oil facilities.