US Defence Secretary Leon Panetta has publicly said for the first time that Pakistan must have been aware about former al-Qaeda chief Osama bin Laden's Abbottabad hideout.

"I personally have always felt that somebody must have had some sense of what was happening at this compound. Don't forget, this compound had 18-foot walls... It was the largest compound in the area."

"So you would have thought that somebody would have asked the question, 'What the hell's going on there?'" Panetta added.

Insisting someone in authority in Pakistan must have known where Laden was hiding before US forces traced him, he said that the Pakistani authorities were not informed about the raid over concerns that the killed terror chief would be cautioned.

Intelligence reports had found that Pakistani military helicopters had earlier passed over the compound in Abbottabad, where US Navy SEALs ultimately discovered and killed bin Laden last year, he said.

He also said that a Pakistani doctor, Shakil Afridi, provided key information to the US in advance of the successful raid on Laden's compound last May, The Dawn reports.

Afridi ran a vaccination program for the CIA to collect DNA and verify bin Laden's presence in the compound, and has since been charged by Pakistan for treason. Panetta said he is "very concerned" for the doctor. (ANI)