At least 17 people were killed in a car bomb blast at an opposition checkpoint in the northern Syrian province of Aleppo on Thursday.
The blast hit near the town of Azaz, close to the border with Turkey, the Britain-based Syrian Observatory for Human Rights said, adding that 14 of the dead were Huthi fighters.
It was unclear whether the three others among the dead were civilians or rebels.
The attack injured dozens and the monitor said the toll could rise further because of the number of people with serious wounds.
The checkpoint was run by the Shamiya Front rebel group, which is active in Aleppo province, and was on the road to the Baby al-Salama crossing.
The Islamic State group has regularly targeted rebel factions with bomb attacks, including an October 6 attack at a border crossing in neighbouring Idlib province that killed 29 rebels.
More than 300,000 people have been killed in Syria since the conflict began with anti-government protests in March 2011.
