British prosecutors on Tuesday charged two 24-year-old men from London with national security offences. The case is linked to suspicious activity near Fairford air base in Gloucestershire, south-west England, which US bombers use for strikes on Iran.
A week earlier, also on a Tuesday, police detained two men in the case. Before that, on 27 September, armed officers arrested five men in three cars near the base. They found petrol in the cars but no explosives. People living nearby were evacuated, and the bombers were moved out soon afterwards over security fears.
How it began: Two more arrested over Fairford air base case, police suspect Iran
One of the men is charged with conduct likely to give material help to a foreign intelligence service. Prosecutors say it ran from 31 August to 28 September.
The other is charged separately with approaching or entering a prohibited place on 22 August for a purpose that is alleged to harm UK national security. Both are due to appear at Westminster Magistrates' Court later on Tuesday.
Assistant commissioner Laurence Taylor, who leads UK counter-terrorism policing, said investigators believe Iranian state involvement is highly likely. He added that the exact nature and aim of any operation are still being investigated.
Prosecutors said neither man has been found guilty of any crime.
Five other men detained during the investigation remain on police bail.