Fighters from a shadowy militant group with suspected links to al-Qaeda joined Syrian rebels in seizing a government missile-defense base in northern Syria on Friday, according to activists and amateur video.

It was unclear whether the rebels were able to hold the base after the attack, and analysts questioned whether they would be able to make use of any of the missiles they might have taken.

Nevertheless, the assault underscored fears of advanced weaponry falling into the hands of extremists, whose role in Syria’s civil war appears to be increasing.

Videos purportedly shot inside the base and posted online stated that the extremist group Jabhat al-Nusra participated in the overnight battle near the village of al-Taaneh, three miles east of the country’s largest city, Aleppo. The videos show dozens of fighters inside the base near a radar tower, along with rows of large missiles, some on the backs of trucks.

A report by a correspondent with the Arabic satellite network al-Jazeera who visited the base Friday said Jabhat al-Nusra led the attack, killing three guards and taking others prisoner before seizing the base.

Two Aleppo-based activists and Rami Abdulrahman, the pseudonym used by the head of the Britain-based Syrian Observatory for Human Rights, also said Jabhat al-Nusra fought in the battle with other rebel groups but disputed the notion that it took the lead role.

Despite Western opposition to President Bashar al-Assad’s regime, the United States and other countries have cited the presence of extremists among the rebels as a reason not to supply the Syrian insurgents with weapons.

Rebel leaders say that arms shortages mean they will take aid from whoever offers it, regardless of their ideology.

Little is known about Jabhat al-Nusra, or the Support Front, which began asserting responsibility for attacks in Syria earlier this year in postings on jihadist forums often used by al-Qaeda.

Meanwhile, the fallout deepened from the forced landing of a Syrian passenger jet in neighboring Turkey, as Russia said that the plane traveling from Moscow to Damascus was carrying radar parts being transported legally and that the Russian company that sent the cargo will demand its return.

Turkey’s prime minister has said the plane was carrying ammunition and military equipment for the Syrian Defense Ministry.

— Associated Press