(Adds alleged links to militant commander)
MIRANSHAH, Pakistan, July 1 (Reuters) - A U.S. drone aircraft killed eight suspected Islamist militants in northwest Pakistan on Sunday, security officials said.
A drone missile struck a house in the Shawal Valley where militants were reported to be hiding in the North Waziristan tribal region near the Afghan border.
"Two missiles were fired on a house. Eight militants were killed," said a local intelligence official.
Several of the men killed were loyal to Hafiz Gul Bahadur, a top militant leader in North Waziristan, the official said on condition of anonymity.
Bahadur, a commander who is believed to be allied with the Haqqani network and to support attacks against NATO forces in Afghanistan, is said to have an unofficial non-aggression pact with the Pakistani military.
Last week, Bahadur's group said it would act against anyone conducting polio vaccinations in its area, a direct threat to Pakistanis who collaborate with the United States.
A doctor who helped the CIA find former al Qaeda leader Osama bin Laden last year through a vaccination program was sentenced by a Pakistani court to 33 years in jail.
The drone attacks, which fuel anti-American sentiment in Pakistan because they can kill civilians and are seen as a violation of sovereignty, are one of several factors straining ties between strategic allies Washington and Islamabad.
The CIA, which operates the drones remotely, has stepped up strikes in recent weeks in North Waziristan, described by Western intelligence agencies as a global hub for militants.
The escalated campaign means the United States may have obtained information on high-value targets like members of the Haqqani network, one of the deadliest Afghan insurgent groups fighting U.S.-led NATO forces in Afghanistan. (Reporting by Haji Mujtaba in MIRANSHAH, Jibran Ahmad in PESHAWAR, and Saud Mehsud in DERA ISMAIL KHAN; Writing by Michael Georgy; Editing by Ed Lane)