Police investigating the attempted knifepoint abduction of an RAF serviceman have said they are "unable to discount terrorism" as a motive.
Norfolk Police released descriptions of two suspects of Middle Eastern appearance as military personnel were reportedly sent a memo warning them about the incident near RAF Marham on Wednesday.
Detective Superintendent Paul Durham, from the Norfolk and Suffolk Major Investigation Team, said: "I can confirm we are treating this as an attempted abduction and detailed enquiries are being carried out at the scene to establish the full circumstances.
"The motivation for the attack remains unclear at this time, and whilst we are currently unable to discount terrorism, there are a number of other possible hypotheses. We are therefore carrying out a thorough investigation to understand what has happened, why and who is responsible.
"Visible patrols continue in the area and officers will be carrying out house-to-house enquiries and detailed searches of the scene in Squires Hill, which remains closed for the time being."
The serviceman in his late 20s, who had been out jogging, has told police he was approached by two men and attacked but he fought them off.
The first suspect is described as between 20 and 30 years old, about 6ft tall, of athletic, stocky build, with dark hair which was long on top. He had a well-groomed beard, was of Middle Eastern origin in appearance, with a dark skin tone and he wore dark casual clothing.
The second suspect is described as being between 20 and 30 but younger than the first suspect and of a slimmer build. He was approximately 5ft 10in tall, clean-shaven, with short dark hair. He was also of Middle Eastern origin in appearance and wore a white t-shirt and dark shorts.
The suspects are said to have fled the scene in a dark coloured people carrier.
Durham said: "I'm keen to hear from anyone who may have seen the vehicle described above in the King's Lynn area but particularly towards Marham between midday and 6pm yesterday and would urge anyone with information, no matter how insignificant it may seem to them, to call police on 101 or call Crimestoppers anonymously on 0800 555 111."
A note seen by the Daily Mirror and addressed to all service personnel in the wake of the incident warns: "2x Asian males approached a serviceman who was running approximately 1 mile outside of RAF Marham main gate and tried to bundle him into their vehicle.
"The vehicle was a dark-coloured Ford Galaxy. The Asian males were carrying a knife when the serviceman was approached."
A further memo advised military staff to keep a low profile and not to be alone on foot or on a bicycle in any uniform or clothing which identifies them as being with the forces.
An RAF spokesman refused to comment on the memos, and in a separate statement 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 stage."
Norfolk Police also refused to comment on the statement.
One road was sealed off on Thursday and there was a heightened police presence, but the base's Families and Friends Day was going ahead, with hundreds of visitors expected.