U.S.-led troops mounted overnight raids on suspected Al Qaeda compounds in eastern Afghanistan (search), killing four people and detaining several others, officials said Sunday.

The U.S. military said "several Arab fighters" were among the suspects killed or detained in the operation in Nangarhar province, although a local official said only Afghans survived.

The compounds "had clear connections to Al Qaeda (search)," a military statement said.

It said the operation, which was launched partly on the basis of a tip-off from local residents, also netted a haul of weapons, explosives and cash.

Faizan ul-Haq, a spokesman for the provincial governor, said Afghan soldiers as well as Americans took part in the raid in Bati Kot district of Nangarhar.

He said the four people who died were burned beyond recognition, making it impossible to check their nationality.

"We are not sure if they burned themselves before the operation started or if the Americans somehow burned them," ul-Haq said.

Ul-Haq said the five people detained were a man named Syed Rahman and four members of his family.

He said that according to local police, the four people who were killed had been guests at Rahman's house.

Nangarhar lies in a swath of Afghan territory where U.S. and allied Afghan forces continue to battle Taliban-led rebels three years after the fall of the hardline militia.

Foreign militants affiliated with al qaeda are believed to slip into the region from bases on the other side of the nearby Pakistani border.

The area is also heavily cultivated with opium poppies, the source of a heroin trade which the Afghan government says is now the biggest threat to the country's democratic rebirth.