The Central Intelligence Agency, in concert with Pakistan's intelligence service, has conducted a widening campaign against militant leaders inside Pakistan using unmanned Predator drones to conduct air strikes against suspected hideouts.

'Reports of Mehsud's death have circulated in the past, but a US defence official said Pakistani officials appeared to be more certain this time that Mr. Mehsud had been killed,' the report said.

'We don't know 100 percent yet,' an unnamed US defence official was quoted as saying.

'The Pakistanis seem to be a little more confident this time than they have been in the past.'

The US and Pakistan will conduct DNA testing on the body believed to be Mehsud's, using genetic samples taken from members of Mehsud's family, according to the official.

Results could take anywhere from days to weeks.