The blast happened when explosives the men were storing went off, the official said, but residents of the troubled North Waziristan region, on the Afghan border, said a helicopter fired rockets into the house.

"The explosives materials were dumped at the house to make improvised explosive devices," said Syed Zaheer-ul-Islam, top administrator in North Waziristan where the Pakistani army is hunting al-Qaeda militants and their Pakistani supporters.

Three of the dead militants were Uzbeks and two were Pakistani, he said. Two men were wounded, one of them a foreigner, he said.

Residents of the area also said five people, including three foreigners, had been killed, but they said a helicopter fired rockets at the house in Haisori village, about 30km from the Afghan border.