Beirut: Syria`s Al-Qaeda affiliate on Monday seized the key army base of Wadi al-Deif in the country`s northwestern province of Idlib from government forces, a monitoring group said.
"The Al-Nusra Front, backed by (Islamist group) Jund al-Aqsa, seized control of the Wadi al-Deif military base... after a fierce offensive that began yesterday morning," the Syrian Observatory for Human Rights said.
The jihadists` lightning victory in Wadi al-Deif leaves most of Idlib province, which borders Turkey, under Al-Nusra Front`s control.
It is a show of force by the Al-Qaeda branch, which in November drove mainstream rebels seeking President Bashar al-Assad`s ouster from Idlib province.
Mainstream opposition fighters had Wadi al-Deif under siege for around two years, but failed despite repeated attempts to take it over from government troops.
"The jihadists` advance has major symbolic importance, and it also shows the rebels that Al-Nusra Front really is in control of the area," said Observatory director Rami Abdel Rahman.
During its offensive on Wadi al-Deif, "the Al-Nusra Front used tanks and other heavy weapons that it captured last month from the (Western-backed) Syrian Revolutionary Front", Abdel Rahman told AFP.
Al-Nusra`s defeat of the SRF was seen as a blow to US efforts to create and train a moderate rebel force as a counterweight to jihadists.
Idlib province was among the first areas to fall from government control, soon after the 2011 outbreak of a revolt against Assad`s rule.