A schoolboy is undergoing emergency surgery after being stabbed in a shocking attack in Melbourne’s southeast.

The 15-year-old was walking with two friends less than 100 metres from the school gate in Cranbourne South when they were set upon by a group of three hooded youths.

Police said the attack was extremely violent, with the offenders armed with a variety of knives and machetes.

Know the news with the 7NEWS app: Download today

The attackers allegedly charged at the boys, slashing the victim to the back, neck and hands as he struggled to get away.

He managed to escape and made his way back to the school where other students saw him with blood all over his face.

He eventually collapsed on the oval and paramedics rushed him to hospital where he is now having surgery.

The attackers allegedly charged at the boys, slashing the victim to the back, neck and hands. Credit: 7NEWS

Detective Inspector Mark Patrick from Victoria Police described the group’s aggression as they charged at their victim.

“Well, it’s similar to a war cry is when you go into battle and that’s what it would appear to be, is to get their attention and to create fear into their intended victims,” he said.

“It’s an extremely violent attack. You think about long-edged weapons and the reasons that you’re arming yourself with these weapons is to cause serious injury, to cause fear.”

“And it ruins lives, it ruins the victims’ lives and it ruins your own lives if you’re held to account.”

The school says the offenders are not fellow students and it has been supporting the children who witnessed the aftermath.

Police have been patrolling the gates at afternoon pick-up.

The group of three attackers remain on the run.