Syrian rebels killed at least 40 soldiers and other fighters loyal to President Bashar al-Assad as they captured a military base in the northwestern province of Idlib on Wednesday, the Syrian Observatory for Human Rights said.
The anti-Assad monitoring group said the mainly Islamist rebels, including fighters from the al Qaeda-linked Nusra Front, seized al-Shabiba military camp near the town of Nayrab on the main road leading west from Aleppo to the Mediterranean.
The Observatory said al-Shabiba had been used as an artillery base to bombard rebel positions in the region between the towns of Saraqeb and Ariha, attacks which it said had killed hundreds of people.
Fourteen rebels also were killed in the battle for control of the camp and several military checkpoints nearby, which followed two weeks of heavy fighting, it added.
The Observatory, which monitors the violence in Syria through a network of sources on the ground, said the rebel capture of al-Shabiba base was a significant setback for Assad's forces, which have made gains in a series of counter-offensives further south.
Assad's troops, backed by Lebanon's Hezbollah, have been trying to drive out rebels from the town of Qusair close to the Lebanese border, which lies close to strategic supply routes crucial to both rebels and government forces.