Four Canadian soldiers were killed and 10 wounded Thursday in militant attacks and 21 Afghan civilians died in a suicide car bombing, the latest barrage of violence to herald NATO's new security mission in southern Afghanistan, officials said.

Suspected Taliban fighters firing rocket-propelled grenades from a school killed three NATO soldiers and wounded six near the village of Pashmul, west of Kandahar city, a NATO statement said. Canada's military spokesman in Ottawa, Navy Lt. John Nethercott, confirmed the dead and wounded were Canadians and said a local interpreter was also wounded.

CountryWatch: Afghanistan

Hours earlier, two roadside bombs planted on a highway by suspected Taliban militants, also near Kandahar, killed one Canadian soldier and wounded four others, said Maj. Scott Lundy, a spokesman for the Canadian military in Kandahar.

The dead man was identified as Cpl. Christopher Jonathan Reid. The bombings happened on the same stretch of road, three hours apart.

Canadian Department of National Defense spokesman Jay Paxton said the day's fighting and deaths were a "tough task" for the Canadian forces. "But I want to emphasize that today was also a necessary and successful step toward improving security in southern Afghanistan," Paxton said.

Seven foreign soldiers have now been killed since the changeover on Sunday, as an 8,000-strong force of NATO troops, mainly from Canada, Britain, the U.S. and the Netherlands, has assumed command across volatile southern provinces from a U.S.-led coalition.

It is 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 Monday.

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.

In Thursday's deadliest attack, a suicide car bomber detonated a huge explosion in a crowded market near a Canadian patrol in Panjwayi, a town about 15 miles from Kandahar, killing 21 civilians and wounding 13. Police blamed the Taliban.

The blast tore through the main bazaar in the early afternoon, leaving a carnage of body parts, twisted metal and burning shops.

Interior Ministry spokesman Yousef Stanezai said some of the dead were children.

It was one of the deadliest bombings in Afghanistan since the Taliban government was ousted by U.S.-led forces in 2001 for hosting Al Qaeda leader Usama bin Laden.

Maj. Quentin Innis, a military spokesman, said three Canadian vehicles in a logistics convoy were about 200 yards from where the bomb went off but were undamaged. He said it was unclear if they were the target.

At least 14 shops were burned by the blast that left a crater about 5 feet across and 1.5-feet deep. The wreckage of the destroyed car was flung nearly 100 yards toward the district chief's office. Bloodied caps and shoes lay in the road.

"The people who did this use the name of Islam," said Hamayun Khan, 40, said from his hospital bed in Kandahar, suffering shrapnel wounds to his chest and limbs. "They aren't killing police and coalition forces. They are killing innocent people."

After the bombing, there was heavy fighting on the outskirts of Panjwayi.

NATO attack helicopters and fighter planes launched air strikes about 1.2 miles from the town. An Associated Press reporter heard about a dozen big explosions within the space of 20 minutes, and could see smoke rising into the sky.

Panjwayi was the focus of intense fighting last month involving Canadian forces, who make up most of the international troops based in Kandahar. The city the Taliban's seat of power.

The rocket-propelled grenade attack that killed the three Canadians near Pashmul village came as they were "working to improve security" with Afghan forces on the main road leading toward the capital, Kabul, the NATO 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.

In neighboring 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.