A nighttime raid in eastern Afghanistan by U.S. and Afghan troops sparked a gunbattle that killed three people, including two children, and the military said Thursday it is investigating the deaths.

Civilian casualties have incited resentment and demonstrations against U.S. and NATO forces, though officials blame militants who use civilian homes as cover during clashes. President Hamid Karzai has pleaded with Western forces to do all they can to prevent such deaths.

The latest civilian casualties came as U.S. and Afghan troops were raiding a compound suspected of harboring militants belonging to a suicide bombing network. They were fired upon as they approached late Wednesday in Bati Kot district in Nangarhar province, said Maj. Chris Belcher, a spokesman for the U.S.-led coalition.

After the clash, a militant and two children were found dead inside the compound, Belcher said. A woman and another child were wounded, he said.

"It is regrettable that the civilian lives were put in danger by the militants and our sincere condolences goes to the families of the deceased and wounded," said Belcher, noting the military has launched an investigation.

A policeman also was wounded during the raid, said Ghafoor Khan, a spokesman for provincial police chief. Three other men from the house were detained by U.S. troops, Khan said.

Also Thursday, Taliban militants attacked a police checkpoint in Nad Ali district, in the southern Helmand province, killing five officers and wounding three others, said Mohammad Hussein Andiwal, the provincial police chief.

There were no reports of militant casualties, but authorities recovered one of the vehicles used in the attack and an assault rifle, Andiwal said.

In western Farah province, six police officers were killed and two others wounded, and 14 Afghan army troops were missing after clashes with Taliban militants on Wednesday, said governor Muhaidin Baluch.

A large number of Taliban have crossed into Farah from neighboring Helmand province and were still in control of Gulistan district, Baluch said.

Police have battled militants for three days in the area, and several guerrillas were killed, said Baryalai Khan, a spokesman for the provincial police chief.

Violence in Afghanistan this year is the deadliest since the 2001 U.S.-led invasion that toppled the Taliban militant movement from power in the country. More than 5,600 people have died this year due to insurgency-related violence, according to an Associated Press count based on figures from Afghan and Western officials.

In Kandahar province, hundreds of Taliban militants fled from Arghandab district, 15 miles north of Kandahar city, following three days of fighting which left more than 50 militants dead and hundreds of people displaced, provincial Gov. Asadullah Khalid said.

On Wednesday, a provincial police chief said up to 250 militants were surrounded in the area. There was no sign of militants in the village streets Thursday.

Arghandab's villages were quiet as Khalid, accompanied by over 200 Afghan troops and Canadian soldiers, inspected houses and orchards vacated because of the fighting.

The Taliban had moved into Arghandab earlier this week after the recent death of tribal leader Mullah Naqib, who had kept Taliban fighters out of his region.

Tribal loyalties are an important weapon that the government and militants use in their fight. Securing the support of major tribes in the country's traditional south is a key strategy employed by both sides.

"There are no more Taliban, and the people now can come back to their homes and orchards and live a normal life," Khalid said.