NATO forces in Afghanistan say that six of their soldiers have been killed in a single day during their major offensive against the Taliban in the south. Two of those who died yesterday were British. The nationalities of the other four have not been given.<br/><br/>Earlier, reports say a Nato air strike killed seven Afghan policemen in the northern Kunduz province. The officers were mistakenly hit after a joint Nato-Afghan patrol was ambushed by Taliban insurgents. The Nato-led International Security Assistance Force said it was investigating the reports.<br/>