BEIRUT — Syrian rebels have seized control of the Syrian side of a major border crossing with Iraq from the Islamic State group, activists said Saturday.

The Local Coordination Committees said U.S.-backed fighters from the Free Syrian Army’s Southern Front killed one Islamic State fighter and wounded several others in the process of taking the Tanaf border crossing late Friday.

The Britain-based Syrian Observatory for Human Rights, which relies on activists inside Syria, said the FSA fighters crossed into Syria from Jordan to launch the attack.

The Islamic State-affiliated Aamaq News Agency denied the crossing had been captured. The group had controlled the crossing, located in southeastern Syria, since government forces withdrew in May 2015.

Islamic State fighters meanwhile attacked the government’s supply route to the contested northern city of Aleppo, killing 15 soldiers, the Observatory said. Government forces repelled the attack and secured the road, according to the Observatory and SANA, the Syrian state news agency.

SANA said government forces killed dozens of Islamic State fighters in the clashes.