Two explosions hit an Ahrar al-Sham base in a village in east Idlib province of Syria, according to a monitoring group.
At least 14 fighters from the Ahrar al-Sham rebel group in Syria were killed by bomb attacks on Sunday, the Syrian Observatory for Human Rights monitoring group said.
Two blasts hit a rebel base in a village east of Saraqeb in Idlib province, the British-based Observatory reported.
Ahrar al-Sham said in a statement a lone attacker had driven a motorbike up to the building, detonating explosives attached to himself and a bomb on the bike at the same time, killing and wounding dozens of rebels.
It blamed the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) for the attack. There was no immediate claim of responsibility.
Photos on social media showed bloodied corpses and a blackened motorbike outside a small building in the village. The pictures could not immediately be verified.
Idlib is a rebel stronghold, but some insurgent factions have fought among themselves this year, including in clashes that pitted groups aligned with Ahrar al-Sham against groups that joined the al-Qaeda-linked Hayat Tahrir al-Sham alliance.
Syrian government forces have taken advantage of rebel infighting, particularly a separate spat further south near Damascus, to recapture territory from rebels in the six-year conflict.
ISIL is opposed to all sides in the conflict.