US Defence Secretary Leon Panetta on Friday acknowledged what has long been an open secret -- that the CIA deploys armed Predator drones to hunt down Islamist militants.

The US government officially declines to admit to the spy agency's drone strikes, but Panetta -- who served as Central Intelligence Agency director until taking over the Pentagon in July -- made two casual references to the CIA's use of robotic aircraft during a visit to US bases in Italy.

"Having moved from the CIA to the Pentagon, obviously I have a hell of a lot more weapons available to me in this job than I did at CIA -- although Predators aren't bad," Panetta told an audience of sailors at the US Navy's Sixth Fleet headquarters in Naples.

Later at a joint US-Italian air base in Sigonella, Panetta thanked air crews for their role in the NATO air campaign over Libya as he stood in front of a Global Hawk drone, a larger unmanned aircraft that flies at high altitude for surveillance missions.

Panetta cited the important role of drones in the Libya operation, including the Predator drones.

Predators are "something I was very familiar with in my past job," he said.

After Panetta spoke, a Predator drone took off from the base -- right on cue.

The military does not hide its own drone flights in Libya or the war in Afghanistan, in contrast to the CIA's covert missions to take out Al-Qaeda extremists in Pakistan, Yemen and elsewhere.

It was not the first time Panetta has made references to the drone programme, which US officials credit with severely weakening Al-Qaeda.

As CIA director, he once alluded to the drone strikes against Al-Qaeda as "the only game in town".