A 12-year-old has been stabbed in the hand and leg by three other children who were trying to rob him.
The boy was attacked outside Tesco Express in Whitehorse Road, Croydon, south London, shortly before 5pm on Monday after the trio went through his pockets.
He was taken to hospital but his injuries are not classed as life-threatening or changing.
It is the third knife attack involving young people in the area in recent weeks.
Scotland Yard said three boys aged between 12 and 15 tried to rob the youngster outside the supermarket, and ran off towards St James's Road after stabbing him.
One of the trio was white, about 5ft 6in, with blond hair and blue eyes, and was wearing a black woolly hat, dark jacket and grey tracksuit bottoms.
The other two are both black, one around 5ft 2in and the other about 4ft 11in.
Detective Inspector Simon Harding said: "It appears the suspects have attempted to rob the victim and then, after a brief altercation, the victim has then been stabbed twice. The description of one of the suspects is quite distinctive and I have no doubt that someone will know or recognise who this is. I would urge anyone with information to come forward.
"This is the third stabbing involving young people in Croydon over the past couple of weeks and, whilst they are all unrelated, it will understandably cause concern within the community. Overall, knife crime and youth violence in Croydon is on the decrease, but we are not complacent and are working hard to further reduce these.
"Knife crime is an extremely serious offence and young people in Croydon should be in no uncertain terms that if they are caught in possession of a knife then they will face serious consequences. If you are thinking of carrying a knife, or any weapon, then don't."
Anyone with information can call Croydon CID on 101 or contact Crimestoppers anonymously on 0800 555 111.
One of the other two unrelated knife attacks was in the Whitgift Centre in Croydon, when two boys aged 16 and 17 were non-fatally stabbed when a fight broke out on January 14.
In the second, an 18-year-old was left with non-life-threatening injuries after being knifed in Queen's Road, Croydon, in the early hours of Monday morning.
It is being investigated by Scotland Yard's Trident command, which focuses on gang-related violence.