British prosecutors charged two men on Tuesday under the National Security Act over an incident involving RAF Fairford, a military airbase in southwest England previously used by US bombers to launch strikes against Iran.
The Crown Prosecution Service (CPS) said Mohmed Abdulkarim, 24, from London, had been charged with engaging in conduct likely to materially assist a foreign intelligence service.
Nouman Essghir, also 24 and from London, was separately charged with entering a prohibited place for a purpose prejudicial to the United Kingdom on 22 August.
Both men were due to appear at Westminster Magistrates' Court later on Tuesday.
Assistant Commissioner Laurence Taylor, head of National Counter Terrorism Policing, said investigators believed the foreign country Abdulkarim was suspected of assisting was Iran.
The charges follow a major security operation at RAF Fairford on 27 September, when police arrested five British men outside the base in the early hours.
The facility had been used by US strategic bombers to conduct strikes against Iran during the war, although the aircraft were withdrawn on security grounds shortly after the arrests.
British authorities also evacuated residents living near the airbase as police and military bomb disposal specialists examined three lorries suspected of containing explosives.
The vehicles were subsequently found to contain no explosives.
The investigation has continued for several weeks, with authorities examining suspected threats to the military facility and possible links to foreign intelligence activity.
British Prime Minister Andy Burnham had previously said there were strong indications of Iranian involvement in the Fairford incident.
Six others remain under investigation
Frank Ferguson, head of the CPS Special Crime and Counter Terrorism Division, said the decision to bring charges followed an investigation by counterterrorism police into a significant incident involving the RAF base.
He said prosecutors would continue working closely with investigators on what he described as a complex and ongoing inquiry.
Six other men arrested in connection with the investigation have been released on bail and remain under investigation.
Counterterrorism police confirmed on Tuesday that a 25-year-old dual British-Iranian national was among those released on bail without charge.
The CPS stressed that the decision to prosecute did not establish or imply guilt and that the charges would be determined through the criminal justice process.
Prosecutors said their role was to assess independently and objectively whether there was sufficient evidence to bring the case before a court.
RAF Fairford, in Gloucestershire, has served as an important operating location for US military aircraft, including strategic bombers deployed during the US-Israel war on Iran.
The United States had previously announced the withdrawal of its strategic bombers from the facility, with security concerns surrounding the base drawing increased attention following the September incident.
The investigation has also added to tensions between London and Tehran, with Iran previously summoning the British ambassador over allegations relating to the Fairford case.
The two defendants face separate charges under the UK's National Security Act 2023, legislation introduced to address threats including foreign intelligence activity and conduct considered harmful to national security.