A pre-dawn explosion demolished a house in Pakistan's turbulent border zone Thursday, killing at least 12 people, intelligence officials and a local militant said, with conflicting reports of how many are dead.

The blast was reported in a village in South Waziristan, a region bordering Afghanistan where militants linked to Al Qaeda and the Taliban operate. The cause of the explosion was not immediately clear.

One intelligence official, who spoke on condition of anonymity because he is not authorized to speak on the record, said about 10 foreign militants were believed killed.

Six others were wounded in the strike in the village of Kalosha, the official said, citing initial reports from informants in the area. He had no further details of the victims' identity.

The official, based in Dera Ismail Khan, a city near South Waziristan, said the suspects had been staying in the home of a local tribesman.

A second intelligence officer said the explosion rattled the windows of his office in Wana, South Waziristan's main town, about six miles away. He said the nationalities and identities of those killed were unclear.

A local militant fighter, who did not want his name used for fear he might be targeted by security forces, said up to 12 of his guests had been killed. He said they were all Afghan civilians, including children.

The militant said a plane had been heard in the area shortly before the strike and one of the intelligence officials said a U.S. drone may have fired a missile at the house. Pakistani forces were not involved, he said.

A spokesman for the U.S. military in Afghanistan and a spokeswoman for the U.S. Embassy in Islamabad said they had no information about the incident.

South Waziristan lies in a swath of Pakistani territory that has fallen increasingly under the control of militant groups opposed to the American-backed governments in Kabul and Islamabad.

Western officials are concerned that Al Qaeda leader Usama bin Laden and his deputy, Ayman al-Zawahri, have found increasingly secure refuge in the area.

Pakistan says it does not allow U.S. forces to operate on its territory. However, unmanned American Predator aircraft have apparently fired missiles at suspected militant targets on several occasions in recent years. Last month, Abu Laith al-Libi — a key Al Qaeda leader — was killed when a Predator fired on a suspected terrorist safehouse in the north Waziristan region.