Three American service members were killed in a roadside bomb attack in Afghanistan on Tuesday, marking the deadliest day for U.S. forces in the embattled country this year.

Three American troops were killed and three others were wounded in the attack in the notorious Taliban hotbed – Ghazini city – after their armored vehicle drove over a massive bomb buried under the road. An American contractor was also wounded in the attack.

Including Tuesday’s attack, 12 Americans have been killed in combat in Afghanistan this year. Five Americans have been killed this month alone.

The victims in the attack Tuesday weren’t immediately identified.

“In accordance with U.S. Department of Defense policy, the names of the service members killed in action are being withheld until 24 hours after notification of next of kin is complete,” military officials said in a statement.

The Taliban claimed responsibility for the attack, saying a U.S. tank was completely destroyed.

The attacked was the deadliest since June 2017, when an Afghan soldier shot and killed three U.S. soldiers in an insider attack in the Achin district of the eastern Nangarhar province.

Tuesday’s deaths come just days after a U.S. soldier was killed in a firefight with Al Qaeda forces Saturday, defense officials told Fox News.

U.S. Army Ranger Sgt. Leandro Jasso, 25, from Leavenworth, Wash., was wounded by small arms fire while conducting an operation to eliminate Al Qaeda militants in Nimruz Province, located in the southwest part of Afghanistan. Jasso was evacuated to Helmand province, where he was pronounced dead, officials said.

The Pentagon said the incident remains under investigation. Jasso was the ninth American killed in action in the country this year, and the second this month after a former mayor from Utah who served in the state’s National Guard since 2013 was slain in an “insider attack" in Kabul on Nov. 3.

Brent Taylor, a married father of seven children who was deployed to Afghanistan in January, was a former mayor of North Ogden, a city of about 17,000 people located about 46 miles north of Salt Lake City.

The U.S. and NATO formally concluded their combat mission in 2014, but still provide vital support to Afghan security forces, who have been struggling in recent years to combat a resurgent Taliban and ISIS affiliate. Some 15,000 U.S. soldiers are currently serving in Afghanistan.

International forces have also suffered from so-called insider attacks in recent months, in which Afghan soldiers or police have opened fire on them.

Fox News’ Travis Fedschun and the Associated Press contributed to this report.