BEIRUT Islamic State claimed a suicide bombing on a bus in Syria near the Atmeh border crossing with Turkey late on Sunday that the Syrian Observatory for Human Rights said killed at least 32 people.
The bus was carrying fighters from foreign-backed rebel factions, local rebel sources said.
Islamic State militant 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 U.S.-backed groups who were traveling 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.
(Reporting by Angus McDowall and Lisa Barrington in Beirut, Mohamed El Sherif in Cairo and Humeyra Pamuk in Istanbul; editing by Mark Heinrich)