Police are hunting two men after a serviceman was threatened with a knife near an RAF base in Norfolk.
Officers were on patrol around RAF Marham on Wednesday evening after he was threatened with the blade.
Norfolk Constabulary said they would not speculate on whether the incident was related to terrorism, and the county's police and crime commissioner said a "very intensive investigation" was under way.
The incident shares some elements of the attack on Fusilier Lee Rigby, although the serviceman was not injured in Wednesday's incident.
Police said they were called just before 3.30pm to reports that two men armed with a knife had approached the serviceman, who was not in uniform at the time, in the Burnthouse Road/Ladywood Road area of Marham, near married accommodation.
After threatening the man with the weapon they fled the scene in a dark coloured Ford Galaxy.
Streets around the area were sealed off while an investigation took place and the road where the incident occurred stayed closed on Wednesday evening.
Norfolk Constabulary has not issued a description of the men who remained at large.
Lorne Green, Police and Crime Commissioner for Norfolk, told the East Anglian Daily Times that the incident was under "close investigation with an open mind".
"There is nothing at the moment to strongly suggest one motive above another and it is all subject to a very intensive investigation at the moment.
"There is a very close co-operation between the constabulary and the military police, which is ongoing at the moment."
Police officers were carrying out reassurance patrols around the base into Wednesday night.
A Ministry of Defence spokesman said: "We are aware of an ongoing police operation in relation to an incident near RAF Marham. It would be inappropriate to comment further at this time."
Fusilier Rigby was murdered by Islamic extremists Michael Adebolajo and Michael Adebowale outside Woolwich Barracks, south east London, in 2013. The pair first drove into the soldier, who was not in uniform, before attacking him with knives.