A U.S. service member has been killed and another wounded in an attack in eastern Afghanistan, the NATO-led Resolute Support mission says.

A statement said the “apparent insider attack” occurred on September 3, adding that the service member who died was the sixth American to be killed in Afghanistan this year.

Insider attacks, in which members of Afghan security forces or assailants dressed in Afghan uniforms fire on coalition troops, have become less common in recent years.

"The sacrifice of our service member, who volunteered for a mission to Afghanistan to protect his country, is a tragic loss for all who knew and all who will now never know him," said U.S. General Scott Miller, the new commander of NATO forces in Afghanistan.

The statement did not give the identity of the soldier.

It said that said the wounded service member was in a “stable condition.”

The attack comes nearly two months after a member of a U.S. Army training unit was shot dead by an Afghan soldier in the southern province of Oruzgan.

Two other U.S. soldiers were wounded in the attack.

Around 14,000 U.S. troops are currently stationed in Afghanistan.

Miller assumed command of NATO forces in Afghanistan on September 2, replacing U.S. General John Nicholson.

"To be successful, we must continually learn and adapt to the enemy and the environment," Miller said at a ceremony at Resolute Support's headquarters.

"There is no room for status quo," he added. "We cannot afford to be complacent.”

The Western-backed government in Kabul has been struggling to fend off the Taliban and other militant groups since the withdrawal of most NATO combat troops in 2014.