The Wall Street Journal reported two US refuelling tankers that were using the RAF Mildenhall military base diverted to Germany earlier on Monday.
Several other tankers at the base were moved to Germany and other locations later in the day, the report read, citing people familiar with the matter.
According to the publication, the precise nature of the threat to RAF Mildenhall remained under discussion among US officials.
The US upgraded the security posture at RAF Mildenhall and RAF Lakenheath, the report read, citing a US official familiar with the matter.
It was lifted to 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.
"We do not routinely comment on the activity of other nations," a British defence ministry spokesperson said.
"Aircraft and other assets move regularly according to operational requirements."
A US Air Force spokesperson declined to provide details about the movement of assets, but said it happened for a variety of reasons.
Five men were arrested outside RAF Fairford airbase in September over a security incident, with two others arrested later on suspicion of assisting Iranian intelligence.
The incident, which remains largely unexplained, came amid heightened concern about the security implications for Western states of the war between the United States and Iran.
RAF Fairford had been used by US bombers to carry out strikes on Iran.
British Prime Minister Andy Burnham last month said the activity at the airbase was likely to have been coordinated in Iran.
While Tehran's ambassador to Britain has denied such accusations, Iran's Revolutionary Guards said in July that the Fairford base and any other base used to launch attacks against Iran were legitimate targets.
26°C