Suspected U.S. missiles killed four people Wednesday in an Al Qaeda and Taliban stronghold in northwest Pakistan, intelligence officials said, amid signs of greater cooperation between Islamabad and Washington.

The three missiles hit a compound and a vehicle in Dargah Mandi area of North Waziristan tribal region.

The identities of the dead were not immediately clear, said intelligence officials, who spoke on condition of anonymity because they were not authorized to speak to media. However, the area hit was a stronghold of the Haqqani network, an Afghan Taliban faction that is considered a major threat to U.S. troops across the border in Afghanistan.

Authorities recently confirmed that another missile strike had killed Mohammad Haqqani, a son of the network's aging leader, Jalaluddin Haqqani.

The missile strikes have been one of several blows in recent weeks to militants on Pakistani soil. At least three Afghan Taliban commanders have been captured in recent weeks in Pakistan, including the No. 2 leader of the insurgents, Mullah Abdul Ghani Baradar.

Those arrests were the result of intelligence breakthroughs, U.S. Gen. David Petraeus, who oversees the war in Afghanistan, told reporters in Islamabad on Tuesday night. There are also are unconfirmed reports of another Taliban leader, Mullah Kabir, being arrested.

Petraeus dismissed the idea that Pakistan acted against Baradar and the others because they may have been involved in talks with the Afghan government and it wanted to get a seat at the table by arresting them.

"I wouldn't share your characterizations that, in a sense, (the Pakistanis) have always had this intelligence," he said. "What has happened is that there has been some important breakthroughs."

Over the past 18 months, Pakistan has undertaken several army offensives in the northwest against Islamist militants. Those operations have mostly targeted militants attacking the Pakistani state, not militants fighting U.S. and NATO troops in Afghanistan.

Petraeus said Pakistan still made distinctions between such groups, but that there appears to be an "evolution" in that it now sees them as increasingly entwined.

The insurgents have found ways to retaliate beyond suicide attacks.

Earlier Wednesday, the bodies of two men alleged by militants to be U.S. spies were discovered in Mir Ali, a town in North Waziristan.

Each had a note attached accusing the victim of spying for the Americans and warning other informants they faced the same fate, area resident Akram Ullah said. Another witness, Sana Ullah, said one man was a local tribal elder and the other was Afghan.