WASHINGTON — A Special Forces soldier died Sunday after being injured last week by a roadside bomb in southern Afghanistan, the Pentagon said Monday in a statement, bringing the total number of American troops killed this year in combat in Afghanistan to five.

Last Tuesday, Sgt. First Class Reymund Rarogal Transfiguracion, 36, of Waikoloa, Hawaii, was working alongside Afghan commandos in the Musa Qala district of Helmand Province when he was killed by the bomb, which also wounded several Afghans and at least one other American, according to two military officials.

The Pentagon said it was investigating the explosion.

Sergeant Transfiguracion was assigned to the Third Battalion, First Special Forces Group based out of Joint Base Lewis-McChord in Washington State, according to a biography released by the Army. He was born in the Philippines and enlisted in the Hawaii National Guard less than two months before the Sept. 11, 2001, attacks.

The attack in Musa Qala — one of the most violent districts in Helmand Province at the height of the American troop surge in 2010 and 2011 — came only days after a Marine in the neighboring Sangin District was shot in the head while at his guard post, according to two military officers familiar with the shooting. The bullet glanced off the Marine’s helmet.