Suspected U.S. drone kills three Yemen militants: official ADEN (Reuters) - A suspected U.S. drone attacked a convoy of Islamist militants in eastern Yemen overnight, killing three people, a local security official said on Thursday, as Washington intensifies its aerial campaign against fighters linked to al Qaeda. The official said the rocket hit the convoy in the Shibam area of the eastern Hadramout province and there was a series of explosions from a vehicle believed to be laden with explosives. Residents of the area told Reuters its three passengers were members of a militant cell. The accounts could not be independently verified. The United States has increasingly used drones against militants after they seized swathes of territory in the south of the country during a year of political upheaval that eventually toppled President Ali Abdullah Saleh. Militants calling themselves Ansar al-Sharia (Partisans of Islamic Law) have launched a series of deadly attacks since President Abd-Rabbu Mansour Hadi took office earlier this year vowing to hunt down the group. But many say U.S. drone attacks, which have often killed civilians and are deeply resented by Yemenis, may do more harm than good, potentially discrediting Hadi as a lackey of Washington and turning the wider population against him. A Yemeni army offensive is under way in southern Abyan province, where troops backed by tribesmen on Wednesday captured a strategic mountain that controls access to two militant-held cities. Reporting by Mohammed Mukhashaf; Writing by Isabel Coles; Editing by Andrew Roche