UK police say they have re-arrested two men on suspicion of assisting a foreign intelligence service as part of their investigation into activity at the RAF Fairford air base last month.
Counter Terrorism Policing said in a statement that they had re-arrested a 24-year-old UK citizen who was initially arrested outside the military base in southwest England in the early hours of September 27.
Police said they had also arrested a 25-year-old UK-Iranian dual citizen who had previously been arrested in London.
Assistant Commissioner Laurence Taylor, Head of National Counter Terrorism Policing in the UK, said "we consider it highly likely that there is Iranian state involvement".
UK Prime Minister Andy Burnham last week said that the activity at RAF Fairford, which had been used by US bombers to carry out strikes on Iran, was likely to have been co-ordinated in Iran.