Two U.S. troops and two American civilians were killed, and three service members wounded, in a suicide bombing attack in the northern Syrian city of Manbij on Jan. 16. ISIS claimed responsibility for the attack, which also killed upwards of 15 civilians, but details were still developing in the hours following the bombing.

Note: This story has been updated since it was originally posted, and it is still developing.

BEIRUT — The U.S. military says a number of service members were killed Wednesday in an explosion while conducting a routine patrol in Syria — the first instance of U.S. casualties since President Donald Trump announced his intention to withdraw troops from the country last month.

The Islamic State group claimed responsibility for the rare morning attack in the U.S.-patrolled town of Manbij in northern Syria, saying one of its members carried out a suicide attack and detonated his vest filled with explosives.

Videos released by local activists and news agencies showed a restaurant that suffered extensive damage and a street covered with debris and blood. Several cars were also damaged. Another video showed a helicopter flying over the area.

A local town council and a Syrian war monitoring group said the blast occurred near a restaurant near the town’s main market, near a patrol of the U.S.-led coalition, killing and wounding more than a dozen people.

The Britain-based Syrian Observatory for Human Rights said 16 people were killed, including nine civilians, and others were wounded in the blast. It added that at least five U.S.-backed Syrian fighters were also among the dead.

The attack came days after the U.S. began the process of withdrawing from Syria, pulling out equipment from the northeast into neighboring Iraq. Trump abruptly announced his intention to rapidly withdraw the 2,000 troops from Syria just before Christmas, declaring the Islamic State group to be defeated.

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U.S. Army Col. Sean Ryan, a spokesman for the Inherent Resolve coalition, confirmed that U.S. service members were killed while conducting a routine patrol in Syria. He added that military officials were continuing to gather information about the incident.

U.S. service members were killed during an explosion while conducting a routine patrol in Syria today. We are still gathering information and will share additional details at a later time. — OIR Spokesperson (@OIRSpox) January 16, 2019

Trump’s announcement took some of his closest aides by surprise, upset allies in the region, and led to the resignation of Secretary of Defense Jim Mattis. Since then, U.S. officials and Trump himself have suggested the withdrawal would be slower than initially thought.

The Kurdish Hawar news agency, based in northern Syria, and the Observatory, which monitors the war through activists on the ground, reported U.S. troops were among the casualties.

Turkey's state-run Anadolu Agency, citing unnamed local sources, said a number of U.S. soldiers were injured in the blast and that the U.S. military evacuated soldiers by helicopter.

It was not the first time that forces of the U.S.-led coalition were subjected to attacks in the area, although they have been rare.

In March last year, a roadside bomb killed two coalition personnel, an American and a Briton, and wounded five in Manbij.