WASHINGTON, Jan. 18 -- The US Department of Defense on Friday confirmed the identities of three Americans who were killed in a bomb attack on Wednesday in Syria's northern city of Manbij.

The Pentagon identified the victims as one soldier, one sailor and one Defense Department civilian who were supporting Operation Inherent Resolve, the military intervention by the US-led coalition against the Islamic State (IS).

It was reported earlier that four Americans were killed and three others wounded in the suicide attack, which killed about 20 people.

The IS militant group has claimed responsibility for the attack, which occurred weeks after Washington's decision to withdraw troops from the war-torn country.