Pakistan Didn't Know About CIA House in Abbottabad

The CIA conducted surveillance on Osama bin Laden from a safe house down the road in the Pakistani city of Abbottabad, where bin Laden was killed Sunday, CBS News has confirmed.

A U.S. government source told CBS News' Chris Isham that Pakistani authorities are stunned -- and concerned -- that the U.S. was able to maintain the secret safe house without the knowledge of the ISI, Pakistan's federal intelligence service.

Under former Pakistani President Pervez Musharaf, the CIA was largely dependent on ISI for intelligence and conducted few, if any, unilateral intelligence operations. Now the U.S. is expecting Pakistan to push back further against any U.S. intelligence presence there.

The CIA and the ISI have worked closely together since the Sept. 11 terrorist attacks to hunt down al Qaeda operatives sheltering in Pakistan. But U.S. officials have often voiced suspicions that elements of the ISI were either linked to or supporting militants even as the two countries publicly talked of their alliance in the campaign against extremism.

The CIA safe house was part of an all-encompassing U.S. intelligence operation that ramped up after the discovery last summer of the suspicious compound that turned out to be bin Laden's.

The effort was so extensive and costly that the CIA went to Congress in December to secure authority to reallocate tens of millions of dollars within assorted agency budgets to fund it, U.S. officials told the Washington Post.