Canadian and Afghan forces killed as many as 27 militants and captured three in fighting throughout Afghanistan over the weekend, and Afghan army sergeant also was killed, officials said Monday.

Three suicide car bombs Monday injured a U.S. soldier, another coalition soldier and an Afghan boy, officials said.

A fourth would-be suicide bomber detonated his explosives prematurely Sunday evening, injuring two militants nearby, a police official said.

Supporters of the hard-line Islamic Taliban militia ousted from power in a U.S.-led invasion in late 2001 have stepped up attacks in recent months, principally targeting international and Afghan government soldiers. Four suicide bombings in a 24-hour period is rare in Afghanistan, however.

A coalition patrol on Saturday killed between 15 and 20 militants carrying assault rifles and grenade launchers, who were "moving with the intent to set up an ambush" in Helmand province in southern Afghanistan, a military statement said.

No coalition forces were hurt, it said.

Lt. Tamara Lawrence, a spokeswoman for the U.S.-led coalition, said the coalition troops were Canadian. Americans and British forces also are deployed in the volatile south of Afghanistan, a hotbed of Taliban activity.

CountryWatch: Afghanistan

On Sunday, the Afghan army killed four militants and arrested another in a two-hour gunbattle in Uruzgan province, which sits north of Helmand province, said Gen. Rehmatullah Rausi, Afghan army commander for the southern provinces. No government forces were hurt.

Also Sunday, in the eastern part of the country, soldiers killed three militants and captured three more during a clash in Kunar province. Gen. Zaher Azimi said Afghan troops killed the militants during an operation about 125 miles east of the capital, Kabul.

Militants also shot and killed an Afghan army sergeant in an ambush on his convoy Sunday in Kapisa province, north of Kabul, Azimi said.

On Monday, a suicide car bomb exploded near a U.S. convoy on a highway in southern Kandahar province, wounding a soldier and damaging a vehicle, a military official said.

The wounds suffered by the American were not life-threatening and he was moved to a base in Kandahar city for treatment, said Maj. Quentin Innis, a Canadian military spokesman for the coalition forces in the region.

Meanwhile, a suspected Taliban suicide car bomber detonated his explosives near a coalition convoy in Uruzgan province, provincial police chief Rozi Khan said.

One coalition soldier and one Afghan passer-by, a boy, were hurt. Innis said the soldier's injuries were minor but that he couldn't release his nationality.

In Helmand province, a suicide car bomber struck Monday near an Afghan army convoy in Greiskh district, but no one in the convoy was hurt, Rausi said.

Another suicide attacker's bomb exploded prematurely in southeastern Afghanistan Sunday evening, killing him and wounding two other militants.