Four Nato soldiers were killed and ten wounded in roadside bombings and a militant rocket-propelled grenade attack in the latest barrage of violence to herald the alliance's historic move into southern Afghanistan.
In the same province of Kandahar, a suicide car bomber detonated a huge explosion in a crowded market near a Nato patrol, killing 21 civilians and wounding 13.
In neighbouring Helmand, police backed by Nato war planes, attacked a group of Taliban, killing or wounding 22 of them, a provincial police chief said. Police recovered the bodies of about 10 militants from the battlefield.
Nato officials identified one of the dead soldiers - killed in an early morning roadside bombing - as a Canadian, but there was no immediate confirmation of the nationality of the other three who died in an ambush, also near the main southern city of Kandahar.
The Taliban militia has stepped up attacks this year, sparking fighting with foreign and Afghan forces that has left more than 900 people, mostly militants, dead since May - the bloodiest violence in nearly five years.
The violence has escalated this week, as an 8,000-strong force of Nato troops, mainly from Canada, Britain, the US and the Netherlands, has assumed command across volatile southern provinces that have seen the worst of the fighting from a US-led coalition.
Seven foreign soldiers have now been killed since the changeover, seen as the toughest combat mission in Nato's 57-year history. Three British soldiers were killed in a militant ambush on a convoy in Helmand on Tuesday.
In the deadliest attack on the foreign forces yesterday, suspected Taliban fighters firing rocket-propelled grenades from the area of a school killed three Nato soldiers and wounded six near the village of Pashmul, west of Kandahar.
Nato and Afghan forces came under fire as they were "working to improve security" on the main road leading toward the capital, Kabul, the statement said.
During the operation, Nato and Afghan security forces "inflicted severe casualties on the insurgents and disrupted their leadership in the Pashmul area," it said, without giving further details.
The wounded were evacuated for treatment but none were in a life-threatening condition.
Hours earlier, two roadside bombs planted on a highway by suspected Taliban militants, also near Kandahar city, killed one Canadian soldier and wounded four others, said Maj Scott Lundy, a spokesman for the Canadian military.
The dead man was identified as Cpl Christopher Jonathan Reid. The bombings happened on the same stretch of road, three hours apart.