The Observatory said the Nusra fighters have controlled the majority of towns and villages of the mountainous region of Jabal al-Zawyia in the countryside of Idlib.
Clashes in the countryside of Idlib have intensified recently between the Nusra fighters and the rival group of "Syria's Revolutionists" and other "moderate" rebel groups which were in control of many villages and towns in the region.
The Nusra Front unleashed an offensive against Syria's Revolutionists in recent days, stripping them of their territory in Idlib countryside. The Nusra fighters have captured many towns around Idlib in recent months in a bid to consolidate their positions in that slice of Syria near the Turkish borders.
Last week, a group of Nusra fighters attempted to infiltrate into the city of Idlib, which is under the government control. The group reached the municipal building but was dislodged by the Syrian troops.
Meanwhile, the Observatory said Syrian helicopters dropped barrel bombs over the town of Iblin in Jabal al-Zawyia, as the ground troops shelled the town by artillery. It added that the Syrian troops also clashed with jihadi groups in the vicinity of the town of Rami in the same mountainous region, with reports of losses on both sides.
The Syrian troops also shelled the town of Marat Masrin in Idlib countryside, the Observatory said, but gave no further details.The city of Idlib remained under the government control, but its countryside has not for a long time.