The U.S. military's top officer has called the problem of rogue Afghan soldiers and police turning their guns on allied troops "a very serious threat" to the war effort in Afghanistan.
Army General Martin Dempsey said the Afghan government needs to take the problem as seriously as do U.S. commanders and officials.
His comments to the Pentagon's own news service, the American Forces Press Service, come after Afghan police killed four U.S. soldiers coming to their aid after a checkpoint attack on September 16 in the southern province of Zabul.
The attack came a day after two British soldiers were shot dead by an Afghan policeman while returning from a patrol in the southern province of Helmand.
This year, 51 international service members have died at the hands of their Afghan allies or those who have infiltrated their ranks.
At least 12 such attacks came in August alone, leaving 15 dead.
The rise in such attacks has led to the training of new recruits to the Afghan army and police being suspended.
Meanwhile, Afghan officials said NATO warplanes killed eight women and girls who had gone out at dawn to collect firewood in the remote Laghman Province.
NATO forces spokesman Captain Dan Einert said that the strike killed as many as 45 insurgents but may have also killed five to eight Afghan civilians.
"Protecting Afghan lives is the cornerstone of our mission, and it saddens us when we learn that our action might have unintentionally harmed civilians," said Jamie Graybeal, a spokesman for international military in Afghanistan.
Afghan President Hamid Karzai said in a statement from his office that he "strongly condemns the air strike by NATO forces which resulted in the deaths of eight women." It said the Afghan government was also investigating.
Villagers from Laghman's Alingar district drove the bodies, covered in white blankets, to the provincial capital, Mehterlam.
"They were shouting 'Death to America!' They were condemning the attack," said Laghman provincial government spokesman Sarhadi Zewak.
Based on Reuters, AP and dpa reporting