(CNN) -- A man wearing an Afghan National Army uniform killed a U.S. coalition service member, the U.S. military said Thursday. It was the latest in a string of such attacks.
The incident took place late Wednesday when the person "turned his weapon against coalition service members," the U.S. military said. The person who opened fire was killed by coalition forces who returned fire, the military said.
A U.S. Defense official said the incident occurred near Kandahar. He didn't know the service member's branch of service or if anybody was wounded from the gunfire.
The Afghan and U.S. military are investigating.
It is unclear whether the shooter was an Afghan soldier or an infiltrator wearing the uniform.
But the problem of Afghan troops who have turned their weapons on allied forces -- so-called green on blue attacks -- has intensified this year.
Gen. John Allen, the commander of the NATO-led International Security Assistance Force, referred last month to "an erosion of trust that has emerged from this," but said that the systems the Afghans and ISAF have in place to help stop these attacks before they happen was having an effect.
Allen said ISAF officials were working on a new procedure to check the backgrounds of Afghans who sign up for the army or police force, and the Afghans "have taken a lot of steps themselves."
"They've worked very closely within the national director of security to place counterintelligence operatives inside their schools, inside their recruiting centers, and inside the ranks, the idea being to spot and assess the potential emergence of an individual who could be an extremist or, in fact, a Taliban infiltrator," he said last month..
In some attacks, insurgents have disguised themselves as Afghan soldiers in order to infiltrate bases.
"The Taliban, of course, takes credit for all of them when, in fact, the majority are not, in fact, a direct result of Taliban infiltration," Allen said.
Disputes can arise from cultural misunderstanding, religious and ideological friction or combat stress, said Brig. Gen. Stephen Townsend, director of the Pakistan-Afghanistan Coordination Cell in the U.S. Joint Chiefs of Staff office.
Townsend said cultural training has been vital for U.S. soldiers, and now the Afghan authorities are considering the same to provide a better understanding of Americans.