A teenager was punched when three youths tried to steal his phone.
The 17-year-old was approached by the group at the railway line bridge in Frizinghall Road, Bradford, who asked him for the time.
When the victim pulled out his phone he was pushed against a stone wall and punched as demands were made for his phone.
He managed to get free, but suffered minor facial injuries.
The suspects were described as white, aged 16 to 20.
Two were 6ft and wore dark hoodies and the third was 5ft 6ins to 5ft 7ins and slim, wearing a dark hoodie with the hood up and a light stripe over the shoulders.
Officers believe the incident at about 5.10pm on Thursday may be linked to a robbery which happened about 90 minutes later, when a woman’s phone was stolen after she was confronted by three men at Frizinghall train station.
Detective Inspector Stuart Lyons said: “We are investigating the robbery on the teenager and would appeal for anyone who saw the offence or a group of older teenage men standing in and around the station between 5pm and 7pm to get in touch.
“We know a cyclist may well have seen this group who we believe were hanging around the station for some time and we would appeal to him or any other witnesses to contact DC Deborah Gargon on 101 or Crimestoppers in confidence on 0800 555111.”