An umbrella group of opposition fighters have reportedly seized control over almost all of Idlib province from government forces after launching a major offensive on Friday.

Abu Yazeed, a spokesman for Ahrar al-Sham, one of Syria's most powerful anti-government groups which is also a part of the the Fattah Army coalition, told Al Jazeera on Saturday that the fighters now hold control over "about 99 percent" of Idlib.

The province borders the two key largely government-controlled provinces of Latakia and Hama.

Speaking from Idlib over the phone, he said that since the offensive began on Friday afternoon, the coalition has managed to make sweeping gains, taking Qiasat, a major military compound; Muhambel, a strategically located town on the road to Latakia; and many other districts and villages.

He said only a very few areas remain under government control, notably an airport on the eastern outskirts of Idlib province; the two northern villages of Fua and Qariat; and a couple of army checkpoints.

The Syrian Observatory of Human Rights, a UK-based monitoring group, confirmed Fattah Army's claims.

The monitor, in a statement on Saturday, said the opposition forces took over the largest military checkpoint in Idlib called al-Masara as well as other key army posts.

Abu Yazeed also said at least 40 government troops had been killed in the recent fighting.

Numerous tanks, armoured vehicles and a rocket launcher were destroyed by the fighters, he said.

The Syrian Observatory reported a lesser death toll of 32 soldiers, adding that 13 opposition fighters were also killed in the clashes.

Syrian state news agency Sana also reported the military's loss of territory in Idlib, saying "the army evacuated several military sites around the town of Muambel".