At 8.20am on Friday (13/11), a boy aged 12 was approached by an unknown offender in Sandy Lane Sports Ground in Blackbird Leys.
The offender grabbed the victim’s arms and reached into his pocket, before taking his mobile phone.
The victim was not injured in the incident.
The offender is described as a white man, between 5ft 8 and 5ft 9ins tall and believed to be aged in his early to mid-twenties.
He was dressed in a zipped black coat with a furry hood, which was up over his head and a light white/ grey colour. He had on blue coloured gloves, black jeans, black Nike trainers, and was also wearing a plain black facemask.
Investigating officer, Detective Constable Rebecca Nightingale, said: “I am appealing for witnesses to this incident of robbery against a 12-year-old boy.
“It was a terrifying experience for the victim, who I am thankful was not hurt during the incident. However this is being investigated thoroughly and I would like to speak to any witnesses that saw this incident, or anyone who has information that could relate to it.
“Additionally, I would like to hear from anyone that recognises the description of the offender.
“Anyone with information is asked to call Thames Valley Police on 101, quoting reference 43200374127. You could also make a report online, or call independent charity Crimestoppers on 0800 555 111 for 100% anonymity.”