BEIRUT: Syrian rebels have taken full control of a strategic crossroads in the northwest that further limits the government's ability to reinforce its troops in second city Aleppo, a watchdog said Friday.

Rebel fighters forced troops to pull back from their last position in the Saraqeb area where the main highways to Aleppo from Damascus and from the Mediterranean coast meet, the Syrian Observatory for Human Rights said.

The rebels now control an area extending 25 kilometres in all directions from the town, the Britain-based watchdog said.

“The army has withdrawn from its last checkpoint in the Saraqeb area,” Observatory director Rami Abdel Rahman told AFP.

On Thursday, the army had already lost control of all but three checkpoints in the area.

The rebels killed at least 28 soldiers during its offensive in the area, the Observatory said.

Video footage that appeared to show some soldiers being summarily executed drew condemnation from international human rights groups.

The rebels had already seized the town of Maaret al-Numan, further south on the Damascus-Aleppo highway, on October 8, in a first blow to the government's ability to resupply its troops in the northern metropolis where fierce fighting has raged since July 20.

Army shelling of rebel-held neighbourhoods of Aleppo killed a young girl early on Friday, the Observatory said.

The watchdog, which bases its reports on a network of activists, lawyers and medics at military and civilian hospitals inside Syria, says more than 36,000 people have been killed since the uprising against President Bashar al-Assad's rule broke out in March last year.