Four Afghan policemen were killed and seven others wounded when a colleague opened fire on them at a checkpoint in Afghanistan's southern province of Kandahar.

The gunman, who joined the police force two years ago, "opened fire on his comrades when they were eating dinner" on Wednesday, said Zia Durrani, a Kandahar police spokesman.

Durrani said the rogue policeman was later shot dead by another officer as he tried to flee.

The Taliban claimed responsibility for the attack in the Zhari district.

The shootings are the latest in a string of recent insider killings, known as "green-on-blue" attacks, in which Afghan soldiers or police turn their guns on international troops or colleagues in the country.

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Another Afghan policeman was killed on Tuesday after opening fire on a NATO delegation at the entrance of Afghanistan's Ministry of Commerce and Industries, the ministry said in a statement.

The gunman was wounded when NATO soldiers returned fire, according to NATO spokesman Michael Lawhorn, and later died in hospital.

No NATO forces were hurt during the incident

Last month, another rogue policeman in Uruzgan province drugged and shot dead 10 colleagues in an attack later claimed by the Taliban.

The Taliban considers Kandahar its heartland, along with neighbouring Helmand province, where poppy production accounts for much of the world's heroin.

Fighters have attacked most districts across Helmand in recent months in an effort to reclaim and protect smuggling routes for drugs, minerals, arms and men.

Source: Agencies