British prosecutors said Tuesday that two men had been charged under the National Security Act in connection with a September incident near RAF Fairford, an airbase used by US forces to launch strikes on Iran.

US bombers were withdrawn from Fairford on security grounds shortly after the arrests immediately after the incident.

What have police said about the Fairford suspects?

The Crown Prosecution Service charged Mohmed A., 24, of London, with engaging in conduct likely to materially assist a foreign intelligence service. Counterterrorism police chief Laurence Taylor said investigators believed the country involved was Iran.

Nouman E., 24, also of London, was charged with entering a prohibited place for a purpose prejudicial to the UK on August 22. Both men were due to appear in court later Tuesday.

Nouman E. was initially arrested near the Gloucestershire base on September 27 and rearrested on October 20.

A separate suspect, a 25-year-old British-Iranian dual national also arrested on October 20, was released without charge over the suspected intelligence offense. He remains on bail following an October 1 arrest on suspicion of preparing terrorist acts. Five other men also remain on police bail.

How did the Fairford investigation begin?

Armed police responded to reports of three suspicious vehicles near the base on September 27 and arrested five men. Scores of residents were evacuated as police and military bomb-disposal experts searched the area for explosives.

Police have said they consider Iranian state involvement "highly likely."

"We have seen a range of incidents in recent months that we believe have been directed by the Iranian state," said Laurence Taylor, head of UK counterterrorism policing.

He said police were working with MI5, Britain's domestic intelligence service, to counter the threat and urged the public to report concerns.

Iran has denied involvement, although it has previously said it considers bases used to attack its territory legitimate targets.

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Edited by: Wesley Rahn