A roadside bomb blast killed four Canadian soldiers Saturday in southern Afghanistan in the deadliest attack against Canadian forces since they deployed here in 2002, the military said.

Canadian military officials blamed remnants of the toppled Taliban government for the bombing, which happened in the village of Gomboth, about 25 miles north of Kandahar city.

"We are pretty confident that it was the Taliban and we knew coming in here that they would be targeting us," Maj. Quentin Innis told The Associated Press.

There was no immediate claim of responsibility for the bombing, but Taliban militants have vowed to step up attacks against coalition and Afghan forces during the spring and summer months.

A four-vehicle Canadian convoy was patrolling in the village when the bomb exploded, targeting the third vehicle, which had four occupants, Innis said. Gunmen then opened fire on the convoy from different directions, drawing retaliatory fire from Canadian forces on the ground before fleeing.

Three of the soldiers were killed at the scene while the fourth died from serious head wounds after being evacuated by helicopter to a military medical facility, Innis said.

Innis identified three of the soldiers as Cpl. Matthew Dinning of Wingham, Ontario; Bombardier Myles Mansell of Victoria, British Columbia; and Lt. William Turner from Toronto, Ontario. Relatives of the fourth soldier did not want his identity released.

The attack was the deadliest against the 2,200-Canadian contingent since they arrived here to take over control of Kandahar from U.S. troops. At least 16 Canadians have been killed in this turbulent country since 2002.

Saturday's attack also caused the biggest loss of coalition life since a Feb. 13 bombing that killed four U.S. soldiers in the central province of Uruzgan.

"This doesn't affect the coalition force's commitment to Afghanistan, but attacks like these obviously affect the troops and no doubt we are going to look at our drills and procedures to make improvements," Innis said.

Canadian investigators returned to the attack scene to inspect the remains of the roadside bomb and search the area for more clues, the military said. No arrests have been made.

Taliban militants have been stepping up bombings and shootings targeting coalition and Afghan forces, particularly across southern Afghanistan in provinces such as Kandahar, a former Taliban stronghold.

Rising violence is a growing concern to nations contributing troops under the NATO mandate, which is increasing its current force of 10,000 troops in Afghanistan to about 21,000 by November as it gradually assumes command of all international forces.

Some 6,000 mainly British, Canadian and Dutch troops have started moving into the region, which hugs the mountainous Pakistani border. The remote, tribal-dominated border region is believed to be a haven for Taliban and Al Qaeda extremists intent on attacking coalition forces.

U.S., Canadian and British leaders have urged Pakistan to seal the porous border region, which Islamabad says it is doing. Some 80,000 Pakistani soldiers are based in Pakistan's North and South Waziristan tribal regions trying to block militants crisscrossing through the frontier into each country.