Attack in Nangarhar

Al Jazeera's James Bays, reporting from Afghanistan, said there was also an attack in the Shirzad district of Nangarhar province.

"There have been civilians that were killed in what Isaf [International Security Assistance Force] is admitting is an airstrike carried out by their aircraft. They say they are investigating the incident.

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"The number of fatalities is not clear but locals at the scene are telling us that 12-24 people were killed as they were taking away the bodies from an earlier attack.

"But there has been no word from the Taliban or official government sources about this incident."

Violence in Afghanistan is at its worst since US-led and Afghan armed groups overthrew the Taliban from power in 2001.

The Taliban, who are largely active in the south and east, have stepped up their attacks in recent months in some areas of the north, which was considered to be relatively safe.

Despite a record number of foreign forces in Afghanistan - standing at some 140,000, backed by thousands of Afghan forces - the Taliban has managed to spread its campaign out of its traditional powerbases and into the north of the
country.

June was the bloodiest month for foreign forces in the nine-year-war with more than 100 troops killed.

Hundreds of Afghan civilians have also been killed this year as they become increasingly caught up in the crossfire.

Kunduz has taken the brunt of the Taliban attacks in the north and the fighters are increasingly using it as a base to launch attacks elsewhere in the region.