Several killed in attack in Afghan south

Three civilians died when the bomber struck a military convoy and five more were shot by troops afterwards, they said.

Nato spokesman Major Luke Knittig said he had no immediate information on casualties.

Asked about the accounts of troops shooting civilians, he said: "We will establish the facts. It is still unclear in what way the troops reacted."

Both Nato and US-led coalition troops are stationed in Kandahar, the heartland of the Taliban insurgency, which has been stepped up this year, including a dramatic increase in suicide attacks, previously almost unheard of in Afghanistan.

Two Canadian soldiers were killed in a suicide car bombing in Kandahar last week.

Meanwhile, the Taliban said on Sunday it had shot down a US civilian helicopter chartered by Nato that crashed in bad weather in southern Afghanistan.

"The chopper has crashed and there have been mortalities. We do not know how many," said Interior Ministry spokesman Zemarai Bashary said, adding that the cause of Saturday's crash in a remote area of southern Kandahar province was not known.