U.S. troops were among those killed Wednesday in an attack in northern Syria, the U.S. military has confirmed to CBS News.

The U.S.-led coalition in Syria, Operation Inherent Resolve, confirmed in a tweet that, "U.S. service members were killed during an explosion while conducting a routine patrol in Syria today."

A U.S. military official confirmed separately to CBS News senior national defense correspondent David Martin reports by Kurdish media outlets that at least two Americans were among the dead in the city of Manbij, not far from the Turkish border, after an explosion hit a coalition convoy.

The U.S. military has not confirmed how many American casualties were among the bombing victims on Wednesday, but at least one report said as many as four U.S. service members were killed. If true, Martin notes that it would be the single largest loss of U.S. life in Syria since American forces were deployed there in 2015. It comes just weeks after President Trump declared ISIS defeated and said U.S. troops were coming home.

White House press secretary Sarah Sanders told CBS News on Wednesday that President Trump had been "fully briefed and we will continue to monitor the ongoing situation in Syria." She referred all further questions to the U.S. military.

Manbij is just 20 miles from the border with Turkey, in an area held by Kurdish forces allied with the U.S. military coalition fighting ISIS. The terror group's self-styled news agency Amaq claimed online that the attack was carried out by a member of the group wearing a suicide vest.