KABUL (AFP) - Nato on Tuesday launched an investigation into the deaths of five soldiers in southern Afghanistan as local officials blamed a "friendly fire" error by a coalition air strike.
The deaths in the restive province of Zabul were the worst single incident for Nato's International Security Assistance Force (ISAF) since five British soldiers were killed in a helicopter crash on April 26.
The most recent major "friendly fire" incident was in March when five Afghan soldiers were killed in an air strike in the eastern province of Logar, provoking fury from the Afghan government.
"I can confirm that five foreign troops were killed as a result of their own bombardment in Arghandab district," Mr Ghulam Sakhi Roghlewani, police chief of Zabul province, told AFP after Monday's deaths.
Mr Mohsin Khan, spokesman for the Afghan army's 205 division, which is deployed in Zabul, also said it was a friendly-fire mistake, adding that one Afghan soldier was killed.
"Our forces were jointly engaged in fighting with militants, and foreign forces called in air support and they mistakenly bombed friendly positions," Mr Khan said.
"I can confirm ISAF suffered casualties. We also lost one solider and one was wounded."
An ISAF spokesman declined to comment on reports that "friendly fire" was responsible.
"The incident is under investigation," he said.
"Five International Security Assistance Force service members died in southern Afghanistan yesterday," ISAF said in a brief statement.
"It is ISAF policy to defer casualty identification procedures to the relevant national authorities."
The United States-led force is winding down operations in Afghanistan after more than a decade of fighting Taleban insurgents.
All of the 50,000 remaining Nato combat troops are due to leave the country by the end of this year, though a small US deployment will remain until the end of 2016 if a long-delayed deal is signed between Washington and Kabul.
The south and east of Afghanistan are the most violent parts of the country as the Taliban wage a guerrilla war against the Kabul government and remaining Nato troops.
Afghanistan is preparing for a run-off election on Saturday that will determine the successor to President Hamid Karzai, who has ruled since the Taleban regime was toppled in 2001.
Former foreign minister Abdullah Abdullah fell short of the 50 per cent threshold needed for an outright victory in April's first round and will face former World Bank economist Ashraf Ghani in Saturday's poll.
Late last month President Barack Obama outlined the US strategy to end America's longest war, saying that the 32,000-strong US deployment in Afghanistan would be scaled back to around 9,800 by the start of 2015.
Those forces will be halved by the end of 2015 before eventually being reduced to a normal embassy presence with a security assistance component by the end of 2016.