Canadian General C.S. Sullivan, deputy director of Joint Operations, was appointed by McChrystal to lead the joint investigation, while a US Air Force officer, a German officer, and a legal advisor would support him, it said.

'An initial assessment conducted at the scene of the incident by McChrystal and several of his senior leadership team concluded that civilians had been killed or injured in the strike,' it said, adding that the probe would take 'several weeks to complete its work'.

'The board's result will be shared with Afghanistan and German authorities to inform their follow-on actions as appropriate,' it said.

German Chancellor Angela Merkel also called for a speedy investigation to determine whether any civilians were killed, while Defence Minister Franz Josef Jung has said that the casualties 'might' include civilians.

A commission appointed by Afghan President Hamid Karzai and a UN team are also conducting separate investigations in the province.