At least 14 of the dead are Syrian opposition fighters, while 25 others have been injured including eight in critical condition.
At least 17 people, most members of Syrian opposition groups, were killed in a car bomb blast near a checkpoint close to the Bab al Salama crossing on the Turkish-Syrian border in northern Syria.
Witnesses said the blast took place near a checkpoint manned by a group of Free Syrian Army's (FSA) Jabhat al Shamiya close to a car depot nearly two km away from the border crossing, a major conduit for traffic between opposition held northern Syria into Turkey.
Rescue workers rushed dozens of injured to the nearby Azaz hospital, one witness said, adding that mosques were appealing to people to donate blood.
The Britain-based Syrian Observatory for Human Rights said that 14 of the dead were opposition fighters. The three others among the dead had not be identified yet.
Among at least 25 injured, eight were in critical condition and taken to Turkish hospitals across the border.
"It was hell with many bodies torn and mangled with metal parts from smashed and charred cars," said Abdullah al-Sheikh, a young mechanic said.
Other reports put the death toll higher but the casualty figures could not be independantly verified.
Daesh has regularly targetted Syrian opposition forces mainly Turkish-backed FSA members fighting alongside other factions in Ankara's offensive, dubbed "Euphrates Shield," to push out the terrorist group from their last northern Syrian enclave.
The latest attack comes one week after a Daesh suicide bomber blew himself up at a border crossing in neighbouring Idlib province killing 29 Syrian opposition fighters.
Daesh is fighting against all sides, including the Syrian regime and foreign-backed opposition groups.
More than 300,000 people have been killed in Syria since the conflict began with anti-regime protests in March 2011.