US Air Force says drones spotted over its military bases in England

British police stand guard at the entrance to the US Air Force base at RAF Mildenhall, Suffolk

LONDON/WASHINGTON (Reuters) -A number of unidentified drones have been spotted over three United States Air Force bases in England over the last six days, U.S. officials said on Tuesday.

"Small unmanned aerial systems were spotted in the vicinity of and over RAF Lakenheath, RAF Mildenhall, and RAF Feltwell from Nov 20 to Nov 26," a spokesperson said in an emailed response to Reuters.

The three bases, two in Suffolk and one in Norfolk, are leased by the USAF from Britain.

Pentagon spokesman Major General Patrick Ryder said that the U.S. military was taking the incidents seriously.

"Installation leaders have determined so far that none of these incursions impact the base residents, the facilities or the assets that we have on those bases," Ryder said.

He said that small drones are fairly common and it was too soon to draw conclusions about whether they were sent by hobbyists or others.

However, a U.S. official, speaking on the condition of anonymity, said it did not appear that the drones were the work of hobbyists and appeared to be coordinated, but added that the U.S. military would continue to investigate.

A spokesperson for Britain's Ministry of Defence (MOD) said they "take threats seriously and maintain robust measures" at defence sites.

"We are supporting the U.S. Air Force response," the spokesperson added.

Citing sources, PA Media reported that British troops have been drafted in to help the U.S. Air Force find out who was responsible for the drones flying over its bases. The Times newspaper said about 60 military personnel have been deployed.

The MOD and the USAF did not immediately reply to a request for comment on the deployment of the troops.

(Reporting by Sarah Young,Catarina Demony, Idrees Ali and Phil Stewart; Editing by Mark Porter)