KANDAHAR, Afghanistan (AP) – More than 40 insurgents were killed Saturday as hundreds of coalition troops, many dropped by helicopter, wrested a desert town from the Taliban and U.S. forces battled militants across southern Afghanistan, officials said.

The U.S. military, meanwhile, agreed to assist an Afghan government probe into reports that a coalition air raid killed civilians Monday in southern Uruzgan province. The military said the operation killed 40 extremists, but residents said at least four civilians died.

President Hamid Karzai also ordered new inquiries into fresh violence in Helmand province – the air assault Saturday on the insurgent stronghold of Sangin and Wednesday’s fighting in nearby Nawzad. At least 29 insurgents died in the two clashes.

Widespread violence across southern Afghanistan has killed about 800 people, mostly militants, since May, according to an Associated Press tally of coalition and Afghan figures. The bloodshed marks the deadliest period since U.S.-led forces toppled the Taliban regime in late 2001.

Before dawn Saturday, more than 300 British paratroopers, backed by hundreds of U.S. and Canadian forces, launched a raid in Sangin, where hundreds of Taliban had massed in preparation for attacks, said coalition spokesman Maj. Scott Lundy.

“Coalition forces killed 10 Taliban and drove the others out, but it is difficult to say if the remainder are still nearby,” Lundy said.

The assault was part of Operation Mountain Thrust, an anti-Taliban offensive involving more than 10,000 U.S.-led troops.

Coalition forces will remain in Sangin until the Taliban threat has been wiped out and Afghan authorities can reach out to impoverished residents to promote reconstruction efforts, Lundy said.

The Sangin Valley is a “natural corridor” for Taliban and criminal movement in southern Afghanistan, plus opium poppy cultivation, with the Taliban believed to use some of the proceeds to buy weapons, Lundy said.

Afghan forces killed eight militants in Sangin on Thursday, the Defense Ministry said.

U.S.-led troops and Afghan soldiers also killed an estimated 31 insurgents in firefights Saturday in Uruzgan province’s Chora district, said Lt. Col. Paul Fitzpatrick.

Separately, American forces pledged to provide all available information to an Afghan government investigation into Monday’s air raid on Uruzgan’s provincial capital of Tirin Kot. The military said that operation targeted “extremists” firing from buildings at coalition forces.

The new investigative report ordered Saturday by Karzai, who has repeatedly deplored coalition military operations that kill civilians, will focus on Saturday’s clashes in Sangin and Wednesday’s air strikes in Nawzad, said Assan Tahiri, a presidential palace official. Tahiri said there were civilian casualties in both areas, and the Afghan government will compensate victims.

One of six air raids in Nawzad destroyed an unused school building from which insurgents were allegedly firing mortars, but the U.S. military said there was no indication any civilians were killed.

The Afghan Human Rights Commission condemned the continued violence in the south.

“The fighting, bombing and military operations impact on the civilian community and are unacceptable for us,” it said in a statement.

In other violence:

– Afghan and coalition soldiers killed two male “foreigners” wearing burqas – the body-shrouding veil worn by many Afghan women – and detained five Taliban in Uruzgan’s Dihrawud district Friday, the Defense Ministry said. The foreigners’ nationalities were not released. Soldiers confiscated an explosives-rigged vest and 16 roadside bombs.

– In Zabul, Afghan soldiers killed four militants Friday after they attacked their convoy, while a Taliban rocket-propelled grenade attack on a coalition supply convoy killed one bystander and wounded a truck driver, Afghan officials said.

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Associated Press writer Paul Garwood in Kabul contributed to this report.

AP-ES-07-15-06 1611EDT