Afghan-on-Afghan violence has killed more troops and police than so-called green-on-blue attacks on coalition forces in Afghanistan, NATO statistics show.
The figures show that Afghan soldiers or police officers killed 53 of their own and wounded 22 others in 35 separate attacks compared with fatal attacks on at least 40 NATO service members this year, The New York Times reported Thursday.
The attacks by Afghans on their own forces are described as green-on-green.
Both categories are called "insider" attacks and Western officials have expressed concern that the numbers have risen significantly in the past two years.
The officials said most attacks on Western forces resulted from outrage or personal disputes and that Afghan-on-Afghan killings largely reflected greater vulnerability to infiltration by the Taliban.
There are concerns about cultural clashes as Afghan forces increase in number, raising the threat from their factional differences, which could get worse after the coalition forces leave by 2014, the newspaper said.
Gen. John Allen, top commander of U.S. and NATO forces, confirmed to Pentagon reporters Thursday that the Afghan-on-Afghan violence is a growing problem.
"Indeed, the Afghan casualties are higher than ours in this regard," he said.
Afghan and U.S. officials have stressed the need for improving the vetting of new army and police recruits, the report said.