Islamic State militants launched two suicide attacks on U.S.-backed Syrian rebels near the border with Iraq, leaving at least 12 dead in the fighting and many wounded, rebel sources said on Sunday.

They said eight Islamic State fighters and four of their own men died.

An attack at midnight on a heavily defended base near the al Tanf border crossing involved at least one explosive-laden vehicle that rammed an entrance to the base. At least two U.S.-backed rebels were killed and scores wounded, a rebel source said.