From bad to worse.

BEIRUT (AP) — A shadowy jihadi group believed to be linked to al-Qaida fought alongside rebels who seized a government missile defense base in Syria on Friday, activists said, heightening fears that extremists are taking advantage of the chaos to acquire advanced weapons.

Videos posted online Friday said to have been shot inside the base said the extremist group, Jabhat al-Nusra, participated in the overnight battle for the air defense base near the village of al-Taaneh, east of Aleppo in northern Syria. 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 had seized the base. The report showed a number of missiles and charred buildings, as fighters covered their faces with black cloths.

Two Aleppo-based activists and Rami Abdul-Rahman, head of the Syrian Observatory for Human Rights, also said Jabhat al-Nusra fought in the battle.

Little is known about Jabhat al-Nusra, or the Support Front, which began claiming attacks in Syria earlier this year in postings on jihadi forums often used by al-Qaida. While neither group has officially acknowledged the other, analysts say al-Nusra’s tactics, jihadist rhetoric and use of al-Qaida forums point to an affiliation.

The base captured Friday is part of the large air defense infrastructure Syria has built across the country over the years, mostly for use in a possible war with archenemy Israel.

Last week, the rebels reported seizing another air defense base outside the capital, Damascus, as well as a base in the southern province of Daraa. Online videos shows them torching vehicles and seizing boxes of ammunition in the Daraa base.

Update: Here’s video taken by the jihadists themselves. They now posses some serious firepower.