Kabul, Afghanistan: A US service member was killed and two others wounded in southern Afghanistan on Saturday in what officials described as an “apparent insider attack.”

The US military, announcing the death in a statement, did not provide further details. The wounded service members were in stable condition, the military said. The name of the soldier who was killed was being withheld so the next of kin could be notified.

A US military officer familiar with the attack said it had occurred at a small base in Tarinkot, a town in Uruzgan province, where roughly 150 soldiers who are stationed in Kandahar often rotate through to train Afghan soldiers. The outpost is one of several in the country where the Army’s Security Force Assistance Brigade is stationed. The unit — tasked with training and assisting the Afghan National Army — is one of the leading elements of the Trump administration’s new strategy in Afghanistan.

The death, the third US military fatality in Afghanistan this year, was a reminder that American soldiers remain in the line of fire, though the war is now largely fought by Afghan security forces backed by US air power.

It also offered a reminder that insider attacks, also known as green-on-blue attacks, have been a recurring problem in Afghanistan, carried out by Afghan security forces loyal to the Taliban or harbouring grievances against US troops. About 150 troops from the American-led coalition have been killed in such attacks during the nearly 17-year-old war, according to data from the US military, with the number of the attacks peaking in 2012.

The assault Saturday is the first insider attack of 2018 against US troops, roughly 14,000 of whom are stationed in Afghanistan. In 2017, there were three such attacks on US forces and one against Romanian troops. In June of that year, three American soldiers were killed in Nangarhar province when an Afghan commando opened fire at a small outpost used in the battle against members of the Islamic State.

In 2012, the Pentagon established the Guardian Angel program, under which US units in Afghanistan assigned personnel to shadow their comrades — often armed and in body armour — when they trained alongside Afghan troops. In some parts of Afghanistan, where the US military has increased its training efforts to curb a resurgent Taliban, at least one Guardian Angel soldier follows every adviser during training missions with the Afghans.

The US forces, which once numbered about 100,000, have drawn down to a smaller training and advising mission. The military also maintains a counterterrorism mission and a robust campaign of air strikes in support of the Afghan forces.

Afghan forces, stretched thin as violence escalates across the country, have been suffering large numbers of casualties.

In addition to the Taliban, which have proved resilient, a new element of the Islamic State has emerged in pockets of Afghanistan, particularly in the east.

The coalition government in Afghanistan has also struggled with public unrest, as it remains bogged down by infighting and faces opposition protests.