The US military has reportedly evacuated aircraft from a second airbase in ⁠Britain after a threat from Iran.

Two US refuelling tankers that were using the RAF Mildenhall military base diverted to Germany on Monday morning, while several other tankers at the base ⁠were moved to Germany and other locations later in the day, according to the Wall Street Journal.

Washington withdrew its bombers from ⁠RAF Fairford airbase in September over ⁠a suspected Iran-linked ​security incident.

The precise nature of the threat to RAF Mildenhall remained ⁠under discussion among US officials, it was reported.

The cabinet minister Lucy Powell said the security of military bases in the UK was constantly under review. She told Sky News she could not comment on live operations, “but we’re constantly keeping the security of our bases under review and, as we’ve seen with other cases recently, we take firm and quick action where we need to”.

A Ministry of Defence spokesperson said: “We do not routinely comment on the activity of other nations. Aircraft and other assets move regularly according to operational requirements.”

The US had upgraded the security threat level at RAF Mildenhall and RAF Lakenheath, the report said, citing a US ‌official familiar with the ‌matter.

The base was placed under Force Protection Condition (FPCON) Charlie, which is the second-highest defensive threat level in the US Department of Defense’s security system ‌and occurs when intelligence indicates a form of terrorist action is likely.

It is understood that, on the ground, there has been no specific threat against the RAF base. No arrests have been made, suggesting the threat seen by the US was more general.

A US Air Force spokesperson said: “US Air Force aircraft rotate between installations and operating locations for a variety of reasons, including training and real world requirements. US military aircraft are hosted in accordance with access, basing, and overflight agreements with our allies and partners. Due to operations security, we will not provide further information on movement of assets.”

Five men were arrested outside RAF Fairford airbase in Gloucestershire in September over a suspected plot to attack the base.

Two men, Mohmed Abdulkarim, 24, and Nouman Essghir, 24, who were not among the men arrested at RAF Fairford, later appeared in court charged under the National Security Act 2023 in connection with the incident. Abdulkarim, from Westminster, was charged with assisting a foreign intelligence service, which police earlier said they believed to be Iran.

The prime minister, Andy Burnham, said ‌last month that ​the activity at RAF Fairford ​was likely to have been coordinated in Iran.

While Tehran’s ambassador to Britain has denied accusations it was involved in any plot against the airbase, Iran’s Revolutionary Guards said in July that Fairford and any other bases used to launch attacks against Iran were legitimate targets.