Canadian soldiers came under fire in Afghanistan, only hours after a Canadian general assumed control of coalition forces in the country's volatile south.

The troops were travelling in a convoy on a highway near Kandahar on Tuesday night when militants detonated a bomb and fired shots.

"The roadside bomb exploded roughly 20 metres in front of the lead vehicle," Capt. Mark Peebles told reporters in Kandahar. "At least one rocket-propelled grenade was launched at the convoy but missed. There are also reports of small-arms fire."

Canadian Brig.-Gen. David Fraser took control of the multinational force in southern Afghanistan on Feb. 28. (CBC photo/Daniel Morin)

He said the Canadian soldiers fired back with machine guns and assault rifles before racing on to their base at Kandahar Airfield.

"Everybody returned home with no injuries," Peebles said.

The attack happened on the same stretch of road where militants attacked another Canadian convoy on the weekend, injuring a soldier.

Canada takes command in southern Afghanistan

A few hours before Tuesday's attack, a ceremony was held at the Kandahar air base as control over the multinational force responsible for southern Afghanistan passed from U.S. Gen. Karl Eikenberry to Canadian Brig.-Gen. David Fraser.

There are 2,200 Canadians along with British, Dutch and U.S. soldiers in the force, which is part of the U.S.-led operation in Afghanistan.

The force's mission includes supporting reconstruction efforts, but Eikenberry offered a dire warning for his successor: "There will be an increase in violence in the spring, and we can forecast an increase in violence in the summer."

Fraser said he agrees with the assessment.

"That minority that's trying to destabilize and terrorize the Afghans and the legitimate authority are going to keep attacking it," he said.

Eikenberry said the militants could be expected to increase their violence in large part because the multinational forces have them on the run and backed into a corner.

Canada recently greatly boosted its troops in Afghanistan. It assumes control over the regional forces at a time when they are becoming much more active in remote areas.

Afghan mission is 'the right thing to do,' says UN envoy

Canadians have already weathered a number of attacks from militants, including a serious one in January that killed diplomat Glyn Berry and seriously wounded three soldiers.

The UN's deputy special envoy, Chris Alexander, was among those who defended the mission in Afghanistan on Tuesday.

"Yes, there will be violence, there will be attacks, but when you change things after terrorists, and extremists and insurgents have had their way for a while, it's always destabilizing," he said. "But people want us to do it and it's the right thing to do."

Canada has committed to keep troops in Afghanistan for another year.

Recent opinion polls have suggested public support for the mission is low, but Defence Minister Gordon O'Connor has said the mission is vital.

He rejected the idea of a vote in Parliament over whether to continue the mission.