U.S.-led and Afghan troops battled suspected Taliban insurgents in southern Afghanistan on Tuesday in ground clashes and airstrikes that left over 100 militants dead, the coalition said.

In eastern Afghanistan, a homicide bomber attacked NATO troops helping to build a bridge, killing three American soldiers, a U.S. official said. The official spoke on condition of anonymity because not all families had been notified.

The battle in southern Kandahar province's Shah Wali Kot district started after the joint force was ambushed by a large group of insurgents who tried to overrun their position several times, before being strafed by airstrikes, the statement from the coalition said.

"Coalition aircraft destroyed the reinforced enemy emplacements and sniper positions as well as two trucks used to reinforce and re-supply the insurgent force," the statement.

More than 100 suspected insurgents and an Afghan soldier were killed, coalition said. The casualty figures could not be independently verified due to remoteness of the area.

Clash also left three coalition and three Afghan soldiers wounded, the statement said. The nationality of the coalition soldier was not disclosed, but vast majority of them are American.

Violence is soaring in Afghanistan. This year more than 3,900 people — most of them militants — have died, according to an Associated Press tally of casualty figures provided by Western and Afghan officials.

Also Tuesday, U.S.-led and Afghan troops raided a house near Kandahar city, killing two suspected militants and detaining five others, a coalition statement said.

Those targeted in the raid were accused of facilitating bomb attacks against coalition and Afghan forces in Kandahar, the statement said. The people detained in the raid will be questioned at a military facility before being turned over to Afghan authorities, it said.

In the Taliban-held Musa Qala district of Helmand province, militants ambushed the joint U.S.-Afghan force Monday, another coalition statement said.

The joint force fought back, targeting militants who were using several compounds and trenches for cover, the statement said. It said about a dozen militants were killed in the clash.

Militants have been running Musa Qala since last year's controversial peace deal between local elders and Afghan government officials, supported by British troops in the province. The deal effectively turned over Musa Qala town and surrounding areas to Taliban control.

Also Monday, coalition and Afghan troops spotted a group of 20 insurgents preparing an ambush in Kandahar province's Shah Wali Kot district, coalition said.

The troops attacked the insurgents and killed seven, while the rest fled, the statement said. There were no reports of coalition or Afghan troops killed or wounded in either clash.

In the eastern province of Nangarhar, a roadside blast hit a vehicle carrying Afghan soldiers on Monday, killing four, a statement from Defense Ministry said.