An Afghan policewoman has shot dead an American adviser outside the police headquarters in Kabul.
The circumstances of the killing were not immediately clear, however the shooting could be another insider attack by Afghans against their foreign allies.
A NATO command spokesman, US Air Force Lieutenant Colonel Lester T. Carroll, said the shooter was taken into Afghan custody shortly after the incident.
"We can confirm that a civilian police adviser was shot and killed this morning by a suspected member of the Afghan uniform. The suspected shooter is in Afghan custody," Mr Carroll said.
The slain adviser was a contractor but the name and nationality of the deceased were being withheld.
Kabul's Deputy Police Chief Mohammad Daoud Amin said an investigation is under way to determine whether the killing was intentional or accidental.
It is not known whether the victim was a military or civilian adviser.
The killing came just hours after an Afghan policeman shot five of his colleagues at a checkpoint in northern Afghanistan late on Monday.
The attacker then stole his colleague's weapons and fled to join the Taliban, said deputy provincial governor in Jawzjan province, Faqir Mohammad Jawzjani.
More than 60 international allies, including troops and civilian advisers, have been killed by Afghan soldiers or police this year, and a number of other assaults are still under investigation.
NATO forces, due to withdraw from the country by 2014, have speeded up efforts to train and advise Afghan military and police units before the pullout.
But the surge in insider attacks is throwing doubt on the capability of the Afghan security forces to take over from international troops and has further undermined public support for the 11-year war in NATO countries.
More than 50 Afghan members of the government's security forces have also died this year in attacks by their own colleagues.
Taliban militants claim such attacks reflect a growing popular opposition to both foreign military presence and the Kabul government.