Four of the men died immediately while the fifth succumbed to his injuries later, the NATO-led International Security Assistance Force (ISAF) said in a statement. It said six other soldiers were injured in Tuesday\'s attack.
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\'It is our understanding that one individual Afghan National Policeman, possibly in conjunction with another, went rogue,\' a British military policeman in Helmand said, according to the Press Association.
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Daoud Ahmadi, spokesman for Helmand\'s governor, said the soldiers were killed in Shina Klay village in the restive district of Nad Ali.
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But a senior police official in the province said a man in police uniform shot the soldiers and then escaped from the area.
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\'We don\'t know if the attacker was a member of a Taliban group or there was some kind of personal motivation behind his act,\' said the police official, who declined to be named.
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He said an Afghan police commander for the Gulbuddin checkpoint, where the incident took place, and another policeman were injured in the shooting.
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The ISAF and the Afghan Ministry of Interior jointly began a investigation into the incident, the alliance said.
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\'We will not let this event deter our resolve to build a partnership with the Afghan National Security Forces to provide for Afghanistan\'s future,\' US General Stanley McChrystal, the commander of NATO and US forces in Afghanistan, said in a statement.
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\'Every casualty suffered in our country comes with profound regret,\' Afghan Interior Minister Haneef Atmar said in the same statement, adding, \'This appears to be an isolated incident.\'
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News reports quoted a spokesman from Britain\'s Task Force Helmand as saying that the soldiers were at a checkpoint at the time of the incident and were fired upon by an Afghan policeman.
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The Britons were training Afghan police in what was described as a \'secure compound\' when the incident took place.
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The deaths bring to 229 the total number of British troops killed in Afghanistan since 2001.
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With nearly 460 foreign soldiers killed, 2009 has become the deadliest year for more than 100,000 international troops deployed in Afghanistan from 42 nations since the ouster of the Taliban regime eight years ago.
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