Islamic State group has claimed a suicide bombing on a bus in Syria near the Atmeh border crossing with Turkey that the Syrian Observatory for Human Rights says killed at least 32 people.
The bus was carrying fighters from foreign-backed rebel factions when the attack happened late on Sunday, local rebel sources said.
Islamic State militants claimed responsibility for the attack in an online statement on Sunday, saying the blast killed 50 fighters from the Failaq al-Sham and the Nour al-Din al-Zinki Movement groups.
The statement said the rebels were from US-backed groups who were travelling to fight Islamic State in northern Aleppo province.
Pictures circulating on social media showed the burnt-out remains of a bus and medics treating wounded people.
Turkey's CNN Turk television reported that the explosion occurred at the entrance to the Atmeh refugee camp in Syria, near the frontier crossing, citing local sources.
The Observatory said it had received reports that two Turkish soldiers had been killed in the attack. Turkish officials were not immediately available for comment.
Syria's Idlib province, where Atmeh is located, is a bastion of the Turkey-backed opposition to President Bashar al-Assad's rule. A multi-sided civil war has raged in Syria for more than five years.