A suicide bomber has killed at least four Canadians in an attack on a Nato patrol in the southern Afghan province of Kandahar, Canada's military says.
Canada has suffered a series of casualties in the south
Many civilians were also hurt when the bomber took a bicycle laden with explosives into a crowd of troops and children in Panjwayi district.
The blast came a day after Nato said it had driven the Taleban from Panjwayi.
Hundreds have died in blasts this year in Afghanistan. Later on Monday, a bomb killed at least two policemen in Kabul.
Police said the explosion in the capital also caused civilian casualties.
'Wounded were running'
The BBC's Lee Carter in Toronto says the fresh Canadian casualties will add fuel to an already divisive debate in the country over the mission.
Thirty-six Canadian soldiers have been killed in Afghanistan since the country first sent troops there in 2002. Most of the deaths have been this year.
Brig Gen David Fraser, who commands Canadian Nato forces in southern Afghanistan, confirmed that other troops had also been wounded in the blast in Panjwayi district, about 25km (15 miles) west of the city of Kandahar.
"The soldiers were conducting a patrol in the area to provide security in supporting the Afghan security forces," he told a news conference.
None of the Canadian injuries was life-threatening, he said.
The attack occurred about 0930 (0500 GMT), the Nato-led International Security Assistance Force (Isaf) said.
Local police said a patrol of Canadian soldiers were outside a school on foot, handing out pens and other items to children when a suicide bomber on a bicycle rode into the crowd.
The explosives were in a crate on the back of his bike, an official said.
One bystander described a horrific scene after the explosion.
"Kids were running towards the Canadian convoy because they were giving out pens and notebooks to the children," Mohammed Karim told the AFP news agency.
"A man riding on a bicycle approached the crowd and detonated in the crowd.
"With the explosion, all the shouting of kids was ended and you could hear cries and people running to all sides. Some of the wounded were also running."
The Taleban said it carried out the attack. A spokesman, Qari Mohammad Yousuf, said the bomber was a young Afghan from Kandahar and promised more attacks.
Nato said on Sunday that at least 400 Taleban fighters had been killed in a two-week operation codenamed Medusa, the biggest offensive since Nato took over southern Afghanistan from US-led forces at the end of July.
The deaths cannot be independently verified.
The blast in Kabul killed two, police said
Isaf commander Lt Gen David Richards said the Taleban had been forced out of the district and the next phase was to maintain security to allow thousands of people who had fled the fighting to return home, and then to start rebuilding and development projects.
The BBC's Alastair Leithead in Kabul says the Nato mission emphasises this aspect, but has been bogged down by fighting over the past six weeks.
The operation in Panjwayi is seen as a major test of the mission's strategy, which is attempting to win the support of local people for the government, our correspondent adds.