DERA ISMAIL KHAN, Pakistan — A suspected U.S. strike killed six people Thursday on the Pakistan side of the Afghan border, a lawless region believed to be a stronghold of Al Qaeda, two intelligence officials said. The identities of those killed in the attack was not immediately known, the officials said on condition of anonymity because they were not authorized to speak to the media. "At present, local Taliban have surrounded the destroyed house, and they are not letting anybody get close to it," said one of the officials. Citing agents and informants in the field, the officials said six...