Afghan President Hamid Karzai is urging Canadian, American, and British forces deployed in his nation to exercise restraint when they target militants in residential areas.

He made the comment after more than a dozen civilians and police were killed in possible "friendly fire" incidents over the weekend.

Last week, coalition and Afghan forces launched a major offensive involving roughly 2,500 troops in the volatile Kunar province bordering Pakistan.

Karzai also ordered Afghan security authorities to launch their own investigation into complaints from villagers that seven locals were killed Saturday when U.S. troops, backed by warplanes and artillery fire, targeted militants in Kunar.

The military said it did not know if the seven were killed by artillery or air strikes or if they were caught in a firefight between U.S. soldiers and militants.

"President Karzai was angered by the deaths of these seven people and demands the military use more restraint in future attacks against terrorists not to harm civilians," said a statement released by his office.

The deaths in Kunar came one day after another possible friendly fire incident.

The Canadian-led military force in the south said Afghan police reported casualties during a Friday attack on rebels.

Six Afghan police officers and 41 militants were killed in the fighting in Sangisar, a desert community 40 kilometres southwest of Kandahar.

"We are investigating the incident and we will work jointly with the government of Afghanistan to determine the events that took place during this fight," Canadian Brig.-Gen. David Fraser said Monday.

Canadian light armoured vehicles and U.S. and British warplanes backed Afghan soldiers and police in the battle, military spokesman Maj. Scott Lundy told The Associated Press.

"It is unclear how many of the six policemen died as a result of fratricide (friendly fire), and some may have occurred from Taliban fire," Lundy said.

In the past, Karzai's government has expressed criticism of what he called heavy-handed tactics by U.S.-led troops, but the coalition has defended its actions, saying militants often take cover among civilians during battles.

Canadian investigators are also probing the death of 22-year-old Canadian Pte. Robert Costall, who was killed during a firefight in Sangin late last month.

Fraser ordered the friendly fire investigation after receiving reports from soldiers involved that they believed they came under fire from their own side.

Some 2,200 Canadian soldiers are serving in southern Afghanistan as part of the multinational force that is under the command of Fraser.