Chancellor Angela Merkel said Tuesday she deeply regrets any civilian deaths in an air strike in Afghanistan last week, as she defended the unpopular mission ahead of elections on September 27.

"Every innocent person killed in Afghanistan Is one too many," Merkel said in a speech to parliament. "Any innocent person killed or hurt, including through German actions, I deeply regret.

"It is important to me as German chancellor to express this today, and to the Afghan people, and I think I say this in all your names," Merkel told deputies, promising a "open" enquiry.

"I will ensure that we will not put a gloss on anything."