A gang of teenage hoodies surrounded a 45-year-old man and slashed his face.
The victim was stopped by six teenagers by Evenlode Tower, Blackbird Leys Road, on Tuesday at about 5pm.
They demanded his mobile phone, but when he refused he was grabbed by the arms and then scratched in the face with what is believed to be glass or a can picked up from the ground.
Three of the youths are white and three black. They are aged 16-18 years old and all were wearing dark clothing and hooded tops.
Dc Jo Holland, of the Oxford Robbery Team, said: "Despite his injuries being minor, this man has been left upset and frightened by this attack in broad daylight.
"It happened at a busy time of day and right outside the Evenlode Tower, so we are hoping someone may have seen this incident and will come forward."
Anyone with information should ring police on 08458 505505 or anonymously to Crimestoppers on 0800 555 111.
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