Seven Afghan police officers were killed today when their vehicle was mistakenly hit by fire from a NATO military plane, dpa cited police and witnesses as saying. Afghan and NATO-led forces began a joint operation against Taliban militants in Emam Saheb district of northern province of Kunduz earlier in the day, district police chief Abdul Qayoum said. "During the operation a NATO jet hit a police ranger and killed seven policemen," Qayoum told the German Press Agency dpa. "We believe the pilot mistook the police forces for Taliban." One police officer was wounded in the attack, he said. Resident Abdul Latif told dpa that one of his relatives, who was a police official, was killed in the attack. "Some of the bodies were torn to pieces and are beyond recognition," he said in an interview at the hospital, where the bodies were taken. Sofi Nazikmir, a member of provincial council meanwhile said local villagers told him that they saw military plane firing a rocket at the police vehicle. A NATO spokesman in Kabul said that the alliance was aware of an incident, and that its forces were investigating. Mohammad Omar, Kunduz's provincial governor said authorities in the region had been asked to probe the incident. The deadly airstrike could strain the relations between the Afghan government and NATO forces at a time when both sides are calling for closer partnership and cooperation in fight against Taliban, who are active throughout the war-torn country. As part of US new strategy to turn the tide of the eight-year-war in Afghanistan, thousands of Afghan and NATO troops, mostly US and British soldiers, began the largest-ever operation in southern province of Helmand to root out Taliban in the last main bastion in the country. The NATO leaders have recently endorsed a new plan to boost up the number of Afghan police and army to 300,000 by summer 2011. The alliance are to send more trainers to accelerate the process.