Counterterrorism police said the men were found inside the perimeter of R.A.F. Molesworth, a base used by the United States, raising concerns about security.
A police roadblock near the R.A.F. Fairford air base. Prime Minister Andy Burnham of Britain said on Wednesday that there were “strong indications that Iran played a part” in the previous weekend’s events there.
The British counterterrorism police said the five British nationals arrested near R.A.F. Fairford on Sunday were being released on bail but remained under investigation.