Two U.S. service members were killed and another two wounded after they came under fire in northern Afghanistan on Thursday, U.S. military officials said.

They were on a mission with the Afghan military to clear a Taliban position and disrupt the group’s operations in the Kunduz district when the incident happened, authorities said.

"On behalf of all of U.S. Forces - Afghanistan, today’s loss is heartbreaking and we offer our deepest condolences to the families and friends of our service members who lost their lives today," Gen. John W. Nicholson, the commander of U.S. Forces in Afghanistan, said in a statement.

"Despite today’s tragic event, we are steadfast in our commitment to help our Afghan partners defend their nation,” he added.

The dead service members' names are expected to be released after their families are informed.

The situation in Kunduz has remained tense since the region’s capital city was briefly captured by the Taliban late last year. It was attacked again by Taliban fighters in October.