The killing of 12 Afghan civilians by stray NATO rockets during the current major offensive against Taliban strongholds in Afghanistan was Monday described as a "very serious setback" by the head of Britain's armed forces, DPA reported.
Air Chief Marshal Jock Stirrup, the chief of the defence staff, said the incident in southern Afghanistan Sunday had damaged the current NATO offensive.
"It is always damaging, but of course in any conflict situation accidents happen and we must remember that most of the civilian casualties are not caused by ISAF (the International Security Assistance Force) or by the Afghan national security forces, they are caused by the Taliban," Stirrup told the BBC.
"It is a very serious setback ... but we are there to provide security for the population," he said.
The civilians were killed when two NATO rockets missed their intended Taliban targets in Nad Ali district.
Stirrup said it was too soon to pass judgement on the success or failure of the current offensive, codenamed Mushtarak, which began at the weekend.
"This is a long drawn-out process in which one has to have stamina and one has to have patience. In about 12 months we will be able to look back and say that this whole operation has been successful," said Stirrup.