A member of the US military was killed and four others wounded during a New Year’s Day combat operation in Afghanistan, officials said Tuesday.

According to the NATO mission in Kabul, the “combat engagement” occurred in Achin, in the restive Nangarhar province in eastern Afghanistan.

“Two wounded service members are being treated at a nearby medical treatment facility and are in stable condition. The other service members have returned to duty,” NATO said in a statement.

Officials did not disclose which branch of the military the troops were from, and no other information was immediately available.

While Afghan security forces are conducting most of the fighting against the Taliban and other insurgent groups, US troops operate alongside them in a training capacity and are frequently on the front lines.

The United States hopes 2018 will see the Afghans finally seize the momentum against the Taliban after years of stalemate.

2017 was a particularly deadly year for Afghans, with the number of civilian casualties on track to be one of the highest on record since an insurgency backed by US air power toppled the Taliban in 2001.

More than 8,000 civilians were killed or wounded in conflict-related violence in the first nine months of last year, according to data compiled by the UN Assistance Mission in Afghanistan.