A 16-year-old schoolboy is fighting for his life after being stabbed on a packed bus in broad daylight outside a Highbury school.

Several onlookers have spoken of their horror as they watched paramedics and police give the teenager CPR on the single-decker which had just driven past Highbury Grove School.

No arrests have been made while the offender remains at large, but one neighbour described seeing a young male running past her home in the opposite direction to which the bus was travelling on Highbury New Park.

Police scoured the nearby Spring Gardens estate in case a knife had been dumped soon after the incident at 3pm.

A Met spokesman confirmed the schoolboy is in a “critical but stable condition” following the incident on the route 393 bus.

Onlookers also described seeing blood pouring from a stretcher which was used to carry the victim from the bus to the nearby air ambulance which landed in the school grounds and airlifted him to hospital.

Lisa Mitchell-Smith, who lives on a ground floor flat of the estate, described seeing a hooded man running down an alleyway which passes her kitchen window.

She said: “I saw a black guy run past the kitchen. I saw him zoom past just before I went and saw that most people were still on the bus. He was wearing a hoody which was pulled up.

“They got the boy to the ambulance by stretcher and there was about six policemen covering him with sheets but you could see blood dripping everywhere beneath onto the street.”

Another witness on the estate, who wished not to be named, but whose flat overlooks where the bus stopped, said police told him the victim has a “1 per cent chance of surviving” and that they attended Highbury Grove School.

Joseph Smith, who also lives on the estate, said: “All I saw was someone reviving somebody in the bus, giving them CPR for about 30 minutes, pumping up and down on their chest.

“They were working on him for ages. I was thinking maybe he died the way they were working on him. It looked like he was losing his fight.

“Police were giving him the CPR waiting for paramedics. It was shocking, just shocking.”

Raffaele Buttice, another resident, said: “I could just see three people on the floor of the bus doing heart resuscitations with CPR.

“It’s just unbelievable. There were kids on there, it was packed, but they were being let off gradually.

“People were standing by in small groups and everything was surprisingly calm. But you just think ‘why’?

“It was probably over nothing. It’s absolutely shocking. These days kids are to quick to reach for a knife or a weapon because they think that is the right way, but it’s just not.”

A Met spokesman said: “Police were called to reports of a stabbing on the route 393 bus at 3.20pm. The bus stopped at Highbury New Park with the junction of Holmcote Gardens.

“London Ambulance Service and the Air Ambulance were called. The victim, a male in his teens, has been treated at the scene. He is in a critical condition.”

A London Ambulance Service spokesman said: “We were called just after 3pm to reports of a stabbing. A boy was treated at the scene and taken by air to hospital.”