WASHINGTON—Islamic State militants attacked American forces and their Syrian rebel allies at a base in southern Syria on Saturday, triggering a fierce fight that required coalition airstrikes to repel, U.S. military officials said Sunday.
The complex attack began on Saturday when Islamic State fighters detonated a vehicle bomb at a base in al-Tanf, a town in southern Syria along the Jordan border used by American special operation forces and Syrian rebels working with the U.S. coalition, the officials said.
Between 20 and 30 Islamic State fighters, including some with suicide vests, then attacked the base, which is a staging ground and training facility for the U.S.-backed Syrian rebels.
There was no word of any American fatalities in the attack.
The Islamic State attack comes as the U.S. military is deepening its presence in Syria as part of an intensifying campaign to drive the extremist group from its de facto capital in Raqqa.
For weeks, the U.S. military has been strengthening its presence along the Jordan-Syria border, according to U.S. and Jordanian officials.
The U.S.-backed forces in southern Syria have made modest gains in the fight against Islamic State. The fighters seized control of an Islamic State-controlled border crossing last year, but they have struggled to make bigger gains.
Both U.S. Special Operations Forces and the Central Intelligence Agency have worked for years with Syrian rebels along the Jordan-Syria border.
Last summer, Russian aircraft bombed two rebel outposts in the area, raising concerns that the strikes could have killed Americans and British forces that work side-by-side with Syrian rebels.
U.S. forces are facing increasing risks in Syria. The U.S. military recently sent hundreds of Marines into northern Syria to help provide artillery support for the intensifying fight for Raqqa. The Marines joined hundreds of elite American troops expected to take on riskier roles in the coming weeks and months.
Last Thursday, at President Donald Trump’s direction, the American military bombed a Syrian regime air base the U.S. said was used to launch a chemical weapons strike in northwestern Syria that killed at least 85 people, including 27 children.
It was the first time the U.S. has intentionally targeted forces loyal to President Bashar al-Assad, and it triggered concerns that the Syrian leader would retaliate. Moscow, which provides Syria with vital military support, denounced the U.S. strike, which hit a base shared with Russian forces.
While the U.S. gave Russia some warning about the attack and intentionally avoided targeting parts of the base where Russians were known to operate, Moscow said it was suspending an 18-month-old agreement used to prevent mistaken clashes with the U.S.-led coalition. U.S. officials said last Friday that the cooperation had not been immediately cut off in the aftermath of the U.S. strike. But they declined to say Sunday whether the deal was still in effect.