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.

The militants also staged a suicide attack on a convoy of rebel fighters from the Western-backed Osoud al Sharqiya rebel group, who had sent reinforcements from their outpost near the Rukban refugee camp further south west. Two of the fighters in the convoy were killed in the ambush.

Islamic State “staged a suicide attack and there were clashes inside Tanf. Two were killed and several injured. They also attacked our convoy but it’s over and matters are under control,” said a senior rebel source from Osoud al Sharqiya who requested anonymity.

Islamic State-affiliated Amaq news agency said two suicide attacks were conducted by its fighters near Tanf on “positions of Syrian groups supported by America.”

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