Shots were fired by US service personnel and a suspect was arrested after a disturbance at RAF Mildenhall.
Suffolk Police confirmed the arrest as the base, which is used by the US Air Force, was put on lockdown amid reports of a car being rammed into a checkpoint.
The force said the suspect had been taken into custody.
He was said to have suffered cuts and bruises during the incident, which happened at around 1pm on Monday.
A Pentagon spokesman in Washington said: “The security incident has been contained and a suspect has been apprehended.”
(PA Graphics)
A brief statement on the base’s Facebook page said: “RAF Mildenhall locked down at 1pm today following reports of a disturbance on base.
“The base was locked down and emergency personnel are responding to the situation.”
A member of staff at Jumppin Jacks Funhouse in Mildenhall told the Press Association: “All the American children playing here suddenly left, but we didn’t hear anything or know why.”
The base has previously been identified as a potential target for terrorists.
In May 2016, Junead Khan was given a life sentence at Kingston Crown Court for planning a strike against American military personnel in Britain.
Khan, of Luton, used his job as a delivery driver to scout bases including Mildenhall and nearby RAF Lakenheath the previous year.
No other police forces are thought to be involved in the incident at this stage.
A spokeswoman for Suffolk Police was unable to confirm whether the matter was being treated as terrorist-related.