Witnesses are being urged to come forward after two men were injured and robbed in incidents in Lynn this week.
Three teenage boys have been arrested and bailed in connection with the second of the attacks, which both happened on Tuesday afternoon.
And detectives have particulaly appealed for two people who they believe may have vital information to come forward.
Police say the first attack happened at around 4.20pm when a man in his late teens was pulled off his bike and attacked on the path between the iron bridge and the Fairstead estate.
He suffered a minor puncture wound, thought to have been caused by a knife to his back and bruising before the gang of four men, who had blocked his path, made off with his bike. The machine was later recovered.
Then, at around 6pm, a man, also in his late teens was attacked as he walked along Gayton Road towards the Queen Elizabeth Hospital.
He suffered head and facial injuries when he was assaulted by a group of three assailants before a bag, containing a laptop computer and headphones, was stolen.
Three boys were arrested in relation to that incident and have been released under investigation to report back to police on April 25..
Investigating officer Det Con Larissa Foreman said: “We are extremely keen to hear from anyone who may have witnessed either incident of has any information that relates to the robberies.
“In particular, we are keen to trace a jogger who may have interacted with the group and a lady who was walking nearby when the incident happened on the black path.”
Anyone with information should contact Det Con Foreman via the non-emergency 101 number.