MANILA: A US drone believed to be used for reconnaissance was recovered on Monday in waters off the central Philippines, police and naval authorities said.

Fishermen found the 3.65 metre (12-foot) drone floating off Masbate island and dragged it to shore, said provincial police chief Senior Superintendent Heriberto Olitoquit.

They had initially thought it was a bomb and alerted police about the unusual discovery, Olitoquit said.

"A technical evaluation determined that the object is one Unmanned Aerial Vehicle," Olitoquit told reporters.

Olitoquit said the drone had been turned over to the Philippine Navy, which would then conduct a thorough investigation of the drone.

"It appears to have been floating for quite some time," Captain Rommel Galang, deputy commander of naval forces in the area, told AFP.

"We will first study this drone but initially it appears to be a UAV used largely in reconnaissance."

He said it had inscriptions and a serial number that "indicate it is an American drone".

Galang said the US embassy had been informed of the discovery and local authorities would eventually turn it over to them.

A spokeswoman for the US embassy was not immediately available to comment.

In an interview with AFP last year, President Benigno Aquino confirmed that the Philippines has been allowing US drones to overfly its territory for reconnaissance flights, but were not allowed to make strikes.

About 600 US forces have been rotating in the southern Philippines since 2002 as part of the US government's global war on terror.

However the drone was found in Masbate, many hundreds of kilometres from the Muslim insurgency-racked areas where no US troops are known to operate.

Masbate is one of the areas where communists waging a decades-long rebellion have long operated.