Six Afghan policemen have been shot dead after being poisoned by colleagues in southern Afghanistan.

The shooting, which is the latest in a series by Afghan security personnel targeting their local and foreign colleagues, occurred in Gereshk district of volatile Helmand province on Thursday.

"A cook and a policeman first food-poisoned their colleagues in their post, and after they fell unconscious they were shot dead," provincial spokesman Ahmad Zeerak said.

He said the policeman involved in the shooting had been arrested but the cook was still at large.

Farid Ahmad Farhang, a provincial police spokesman, confirmed the incident.

The Taliban claimed responsibility for the attack, according to purported spokesman Yousif Ahmadi, who said eight policemen were killed and their weapons seized.

Afghan police are the key force in supporting US-led NATO forces in a war against the Taliban militants.

Afghanistan has witnessed a surge in insider attacks, often by Taliban spies, in which more than 50 foreigners and dozens of local forces have been killed by their colleagues this year.

The unprecedented number of insider killings comes at a critical moment in the 11-year war, as US-led NATO forces plan to hand security responsibility to the Afghans ahead of a withdrawal of combat forces by the end of 2014.

AFP