An Afghan policeman laced food with sleeping pills and then killed nine of his colleagues as they slept Friday, a police officer reportedly said.
The attack in the eastern province of Paktika was the latest in a string of rogue shootings that has also targeted foreign forces.
Two policemen were detained after the attack in Yahya Khil district, while a third officer was missing. It was not clear if the assailant was among the pair detained, said Mukhlis Afghan, the provincial governor's spokesman.
Citing Paktika police chief Dawlat Khan Zadran, The New York Times reported that the assailant, who it named as Assadullah, put drugs in the food served Thursday night.
The man then waited until the drugs began to take effect and then opened fire with an AK-47 assault rifle after midnight Friday, the Times said.
Shooter joins Taliban
The Taliban said that soon after the attack, the assailant came over to the group, bringing a vehicle and weapons taken from the dead policemen.
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"He has joined our mujahedeen," spokesman Zabihullah Mujahid said in a text message to reporters that arrived as news of the shooting emerged.
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A series of attacks on NATO personnel by Afghan soldiers and policemen have stoked fears that the security forces have turned against their western allies, or have been infiltrated by the Taliban insurgents.
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At least 16 NATO soldiers have been killed in a wave of so-called rogue attacks since January, raising questions about the ability of the Afghan forces to take over full security responsibility by 2014, when the bulk of foreign combat troops leave.
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The policemen in the latest attack were members of the Afghan Local Police, a branch of the police which has been set up in villages where the national force is weak.
Paktika is a stronghold of the Haqqani militant group, which has targeted U.S. troops and the Afghan forces working with them.
Reuters contributed to this report.
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