Four teenage boys have been arrested on suspicion of attempted murder after two girls were stabbed in south London.
The Metropolitan Police said they were called to reports of an assault on Norwood Road in Lambeth on Sunday afternoon.
Officers and the London Ambulance Service found two girls, aged 16 and 17, with stab injuries.
The girls, who police said are known to each other, were taken to a south London hospital.
Police said the younger victim's condition was serious but stable and the second victim's injuries "do not appear to be life-threatening".
The girls' families are aware of the attack.
Four boys, all aged between 16 and 17, have been arrested on suspicion of attempted murder and are in custody, police said.
Detective Sergeant Rob Merrett, of the Central South Command Unit, said: "This is a shocking incident involving two young female victims, one of whom remains seriously ill in hospital.
"It has understandably caused considerable alarm in the community.
"I urge anyone who has information, pictures and video that could assist us to make contact immediately."
Anyone with information is asked to call police on 101 quoting reference Cad 4970/25Apr or contact Crimestoppers anonymously on 0800 555 111. 252222 APR 21