KABUL, the alliance said.
A day earlier, an individual believed to be an Afghan Local Police (APL) member shot dead two international troops in the volatile south. A foreign troop returned fire, killing the assailant.
“The incident is currently under investigation,” said a brief statement from ISAF, which neither revealed the exact location of the latest green-on-blue attack nor the victims’ nationalities.
Mostly British, American and Canadian troops are stationed in the restive south, where the Taliban’s largest base in Helmand province late on Friday.
Four foreign soldiers and a policeman were killed in the attack that occurred in the Mizan district of Zabul province, the deputy police chief, Col. Ghulam Gilani Farahi, told Pajhwok Afghan News.
The provincial police chief and other security officials visited the scene to investigate the incident, Farahi said, adding that more details would be shared with the media after the investigation was completed.
Meanwhile, the Taliban said four US soldiers were killed and several others wounded when a policeman loyal to the movement opened fire on them. Several policemen also suffered casualties when US troops returned fire, they added.
On Saturday, two British soldiers were killed when a local policeman opened fire on them in the Greshk district of Helmand. The shooting is currently being probed.
Since the beginning of the current year, 51 foreign soldiers, mostly American, have been killed in 35 insider attacks by Afghan security personnel.