Three men were stabbed on a night out in Manchester city centre, police said.
They were attacked in Piccadilly Gardens where members of the public gave first aid before emergency services arrived at about 01:20 BST.
They were taken to hospital, where a man, 30, remains in a serious but stable condition.
Another man, 51, is stable while the third, 36, was released from hospital. Three boys - two aged 15 and one aged 17 - have been arrested.
They were detained on suspicion of drugs offences, possession of a weapon and assault. They remain in custody for questioning.
A knife was also found at the scene.
Det Insp Patrick Goodrich, of Greater Manchester Police, said: "This knife attack happened when people were out enjoying the city, doing what they should be, having a great time.
"It is devastating that knives are being brought on to our streets and putting lives in danger, now three men who should have been enjoying themselves have ended up in hospital."
He appealed for anyone with information to contact police.