Rebels overran the Taftanaz airbase in northern Syria on Friday, a watchdog told AFP, in a significant advance.
"The fighting at Taftanaz military airport ended at 11:00 am (0900 GMT) and the base is entirely in rebel hands," Syrian Observatory for Human Rights director Rami Abdel Rahman told AFP.
Soon afterwards, the base was raided by government jets, the Britain-based Observatory said.
"Warplanes are bombing Taftanaz military airport in an attempt to destroy it," a statement said.
Capturing Taftanaz is an important gain for the rebels who control vast swathes of Syria's north and east and are battling President Bashar al-Assad's forces in most major cities and on the outskirts of Damascus.
"This is the largest airbase to be seized since the revolt began" nearly 22 months ago, Abdel Rahman told AFP.
The rebels had previously taken the relatively small Hamdan airport in Albu Kamal on the border with Iraq in the east, and Marj al-Sultan military airport in Damascus province.
The Observatory said that the Taftanaz assault was led by terrorists from the Al-Nusra Front, Ahrar al-Sham and Islamic Vanguard battalions. This fact might be of concern to the West, since Al-Nusra is an affiliate of Al Qaeda, believing in the hope of reviving the Islamic Caliphate that will build a Muslim Empire to eventually rule the world.
Al-Nusra is one of 13 factions in the radical Islamist rebel council that announced its secession from the main opposition force several weeks ago.
The Al-Nusra Front was recently blacklisted by the United States as a terrorist organization.
The Observatory told AFP eight soldiers and two regime militiamen were killed in Friday's attack, as were seven rebels. Many soldiers and officers fled the base at dawn.
Government forces managed to evacuate most of the 60 helicopters deployed there, leaving behind 20 that are no longer serviceable, the Observatory said.
The news came as UN-Arab League special envoy Lakhdar Brahimi met Russian Deputy Foreign Minister Mikhail Bogdanov and U.S. Undersecretary of State William Burns in Geneva.
After more than five hours of talks, Brahimi expressed an urgent need to end the conflict, but reported no major progress.
"We all stressed the need for a speedy end to the bloodshed and the destruction and all forms of violence in Syria," he told reporters, according to AFP.
"If you are asking me whether a solution is around the corner, I'm not sure if that is the case," was all he would say when asked if specific progress had been made.
Brahimi is due to brief the Security Council later this month.
Friday's discussions came after Syria accused Brahimi of "flagrant bias," casting doubt on whether he could remain international mediator.
Damascus lashed out at the veteran Algerian diplomat for describing as "one sided" proposals Assad made on Sunday for a "political solution."
In comments to the BBC, Brahimi attacked Assad's plan to keep fighting rebel "terrorists" and ignore opposition groups tied to them.
He also questioned the decades-long rule by Assad's family, remarking that "what people are saying is that one family ruling for 40 years is a little bit too long."
There had been hope that Friday's talks could produce a clearer idea of how to move towards a transitional government in Syria, where the UN estimates more than 60,000 people have died since the March 2011 outbreak of the revolt.
The Observatory put Friday's provisional death toll at 62 -- 23 soldiers, 22 civilians and 17 rebels.
(Arutz Sheva’s North American Desk is keeping you updated until the start of Shabbat in New York. The time posted automatically on all Arutz Sheva articles, however, is Israeli time.)