MIRANSHAH, Pakistan (Reuters) - At least 45 suspected militants were killed by missiles launched by U.S. drone aircraft in Pakistan's northwest, local intelligence officials said on Tuesday, one of the largest death tolls to date in the controversial air bombing campaign.
Coming a day after Washington announced an $800 million delay in military assistance amid worsening U.S.-Pakistan ties, the attacks could exacerbate tension between the two uneasy allies in the war against militants.
The attacks started on Monday night, when remotely piloted drones fired nine missiles into a militant compound and at a vehicle in North Waziristan, killing 25 suspected insurgents, local intelligence officials said.
Another strike hours later in South Waziristan killed five suspected militants.
Then on Tuesday morning, a drone fired two missiles at another compound in North Waziristan.
"The missiles were fired as militants sitting in a vehicle were entering into a house used by them as a hideout," an intelligence official said, adding that 15 militants were killed in the strike. "The house is on fire."
There was no independent confirmation of the death tolls, and militants often dispute official death figures.
It was the second-largest death toll in a day in the unacknowledged U.S. drone campaign against militants in Pakistan's northwest. In June 2009, about 70 suspected militants were killed in a drone attack in South Waziristan.
Most of the strikes have been concentrated in South and, especially, North Waziristan, mountainous tribal regions on the Afghan border that shelter militant groups friendly with Pakistan but who are attacking U.S. and NATO forces in Afghanistan.
"Of course the number of casualties is very high and it will add to the already strained relationship," a senior Pakistani security official told Reuters.
Washington has been pushing Pakistan to mount an offensive against these militant sanctuaries for years, but Pakistan has resisted, saying it must consolidate its gains against Taliban militants elsewhere first. The United States has stepped up drone attacks in response to Pakistan's perceived recalcitrance.
Drone strikes have become one of the most contentious issues in the U.S.-Pakistan relationship. While Pakistan has always publicly opposed the strikes, privately it allowed them and cooperated with the United States determining targets.
But since the May 2 commando raid that killed Osama bin Laden, which Pakistan considers a grievous breach of sovereignty, the powerful head of the army, General Ashfaq Kayani, has called for a halt.
The army said in a statement it would "fight the menace of terrorism in our own national interest using our own resources."
Such comments in the past have been seen as a signal that Pakistan would not bow to U.S. pressure on military offensives, but the statement made no mention of the drone attacks.
Joint intelligence operations between Pakistan and the United States were suspended in late January, after a CIA contractor killed two Pakistanis in Lahore.
Pakistan's Directorate of Inter-Services Intelligence, the powerful spy agency, has said Washington has its own targeting information and no longer relies on Pakistani intelligence.
"There is intelligence sharing between the two sides," the security official said. "But at times they do carry out attacks on their on intelligence. I can't say for sure whether these recent attacks had our input or not, but generally there is intelligence sharing."
More than 135 militants have been killed since the beginning of June in drone attacks, according to Reuters figures and based on statements from local intelligence officials.
The United States this week said it was holding back $800 million in military aid to Pakistan in a show of displeasure over Pakistan's cutback of U.S. military trainers, limits on visa for U.S. personnel and other bilateral irritants.
The Pakistan military said on Monday it could do without the U.S. assistance by depending on its own resources or turning to "all-weather friend" China.
"As far as the suspension of aid is concerned, it is one way of putting pressure on us," the security official said. "I am not surprised that they have suspended it, and I won't be surprised if they resume it soon too."
(Writing by Zeeshan Haider; Additional reporting by Faisal Aziz; Editing by Chris Allbritton and Yoko Nishikawa)