The school friends were attacked in Penrose Street, Walworth, south-east London, after being approached by two older youths shortly before 3pm on Saturday.

Police later arrested a 15-year-old boy close to the scene of the stabbing.

He was taken to a south London police station for questioning but later released on bail pending further inquiries.

Both victims required hospital treatment for their wounds. The 12-year-old was later discharged with minor injuries.

The younger boy was kept in overnight, but his injuries are not serious, police said.

Any witnesses to the incident are urged to contact Crimestoppers on 0800 555 111.