The United States evacuated several military aircraft from a British airbase on Monday following a threat from Iran, The Wall Street Journal (WSJ) reported, citing sources familiar with the matter.

The threat reportedly targeted Royal Air Force (RAF) Mildenhall in England. However, US officials are still discussing the exact nature of the threat, the report said.

Flight tracking data analysed by CNN showed that 10 US refuelling aircraft were moved from RAF Mildenhall on Monday. Four KC-135 Stratotankers were relocated to Spangdahlem Air Base in Germany, while one went to Ramstein Air Base, also in Germany. Four others were sent to Morón Air Base in Spain, and one was moved to Glasgow Prestwick Airport in Scotland.

CNN has contacted the Pentagon for comment on the development.

The US also raised the security threat level at RAF Mildenhall and another British airbase, RAF Lakenheath, to “FPCON Charlie”, according to WSJ and defence publication The War Zone, which cited a US official on Monday.

FPCON Charlie is the second-highest level in the Pentagon's force protection system. It indicates that some form of terrorist activity or targeting is likely.

A spokesperson for the UK Ministry of Defence said that they “do not routinely comment on the activity of other nations.” The spokesperson also said that “aircraft and other assets move regularly according to operational requirements.”

The latest aircraft movement follows another Iran-linked threat last month at RAF Fairford in England. The base had been used by US B-1 bombers to launch strikes against Iran. However, the aircraft were withdrawn on security grounds shortly after five men were arrested outside the base in the early hours of September 27.

British prosecutors later charged two British nationals under the National Security Act in connection with the incident. Police said the two were suspected of assisting Iran.