LONDON (REUTERS) - Four people were feared dead after a United States (US) military helicopter crashed in eastern England during a routine training operation on Tuesday, police and US officials said.

The helicopter was flying from the nearby US air base at RAF Lakenheath when it went down on the north Norfolk coast.

"We can confirm that one of our HH-60G Pave Hawk helicopters went down outside Cley during a low-level flying exercise," a spokesman at the US base said.

"We are still piecing together details."

Norfolk Police said in a statement there were believed to be four fatalities and a 400m area had been cordoned off.

The Lakenheath spokesman was unable to say how many crew had been on board the helicopter during the operation.

"The primary mission of the HH-60G Pave Hawk helicopter is to conduct day or night operations into hostile environments to recover downed aircrew or other isolated personnel during war," the air base says on its website.

Lakenheath is also home to the Europe's only F-15 fighter wing.