KABUL (Reuters) - The Taliban said their fighters killed a U.S. service member in Afghanistan on Monday and posted photographs of a blood-soaked backpack and the identity card of an American soldier to prove it.

The U.S. Defense Department said Michael Goble, a U.S. Army sergeant from New Jersey, died on Monday from “injuries sustained while his unit was engaged in combat operations” one day earlier in Kunduz province.

The incident was under investigation, the Pentagon said.

Zabihullah Mujahid, a spokesman for the Taliban, said they killed the U.S. force member in a blast in the northern province of Kunduz.

“Our fighters killed a U.S. force member and injured an Afghan commando,” Mujahid said in a text message, which included the photographs.

About 20,000 foreign troops, most of them American, are in Afghanistan as part of a U.S.-led NATO mission to train, assist and advise Afghan forces. Some U.S. forces carry out counter-terrorism operations against Islamist militant groups.

More than a dozen foreign force members have been killed in Afghanistan in 2019.

The United States has been in negotiations with Taliban militants over the past year on a deal under which the United States could withdraw its forces from its longest war in exchange for Taliban security guarantees.

This month, U.S. negotiators said they would take a break from the talks after the insurgents launched a suicide attack on a large U.S. base.

Afghan government forces, supported by the U.S. military, have recently stepped up operations against the Taliban in Kunduz.

The Taliban control more territory than at any point since they were ousted from power in 2001.