A 13-year-old boy had his mobile stolen by teenagers during an afternoon walk on Tuesday.
A group of eight white boys saw the victim on Bletchley Road at the junction with Church End Road in Shenley Brook End at 4.30pm.
Two of the gang went up to the boy threatened him. He handed over his mobile and the group walked off.
The boy escaped uninjured but his Sony Experia, which has a cracked screen, was stolen.
The first offender is in his mid to late teens, about 5ft 10ins and of average build.
He was wearing black Nike Air Max shoes, a grey Adidas tracksuit with white stripes and an orange pattern on the front with the hood up, and a black bandana with white spots.
The second offender is in his mid to late teens, about 6ft and slim
He was wearing a black Adidas tracksuit with white stripes and the hood up and a similar bandana.
Det Con Samantha Reynolds said: “I would urge anyone who recognises the description of these offenders, who were wearing quite distinctive clothing, to contact police immediately.
“Perhaps you have been offered a Sony Experia with a cracked screen since Tuesday afternoon or if you have any other information about the incident then call 101.
“If you don’t want to speak directly to the police you can contact Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org.
“No personal details are taken, information is not traced or recorded and you will not go to court.”