About 20 youngsters – described as moshers or goths – had been enjoying music and having a barbecue when they were viciously assaulted just before 1am yesterday.

Police have launched a major investigation into the violence and have arrested two youths and a man on suspicion of robbery and attempted murder.

The victims, who are friends and live across Leeds, were camping overnight at a country park close to the John O'Gaunts estate in Rothwell, east of Leeds, when four of them were stabbed in unprovoked attacks.

Two of the girls in the camping party were robbed at knifepoint and two of the four victims suffered serious injuries.

One, a man aged 26, suffered life-threatening injuries and had his ear sliced off.

Police said the attacks happened at different locations in the John O'Gaunts area, a small council estate on the edge of Rothwell country park, a former colliery site covering 50 acres.

The most violent of the incidents is thought to have happened outside the Rose Lunn community centre, where bloodstains could be seen on paving.

Police evidence bags could be seen wrapped around large sticks outside the centre.

Those arrested are two 17-year-olds and a man aged 21. They were being interviewed by detectives yesterday and are believed to be local.

Det Supt Bill Shackleton, who is leading the investigation, said: "This is a very serious incident which has left three people in hospital. We would ask anyone who has any information or who witnessed any part of this incident to contact the police."

Police were alerted by a 999 call from a frantic member of the camping party at 12.45am. West Yorkshire Police then scrambled the force helicopter and officers were sent to the scene.

The man aged 26 was rushed to Leeds General Infirmary with serious head injuries.

One other young man suffered serious injuries and another was described as being "walking wounded", while a fourth had less serious wounds.

It is believed the group were goths from various parts of Leeds who may have met at the Corn Exchange in the city centre at some stage and decided to go camping together on Wednesday evening.

They had travelled to the country park at around 8pm before setting up three or four tents and sitting around drinking, having a barbecue and listening to music.

Yesterday afternoon there was a large police presence on the estate, and the country park and community centre were sealed off with police tape.

Residents said they were horrified by the attacks and the use of knives.

Frankie Benson, who lives close to the scene, said: "I heard they were stabbed and someone had their ear chopped off. It is very scary. I have lived on this estate all my life and this is not normal."

Juliette Howick, 31, who lives yards from the crime scene, was woken by the police helicopter in the early hours. She said local people often camped on the fields.

Mandy Smith, 41, a housewife who lives locally, said: "There must have been about 15 youths camping out there. They looked like they were moshers or goths. At about 4am I woke up and there were police everywhere.

"There was four police cars, dogs, three vans and loads of unmarked cars with CID in them."

She was horrified to learn that one of those attacked had serious head injuries. "I heard one of the lads had his ear cut off. I think it's disgusting. I feel sorry for the parents."

Anyone with information is asked to contact police at Holbeck on 0845 606 0606 or Crimestoppers anonymously on 0800 555111.

Any witnesses to the incident are asked to contact Holbeck Police Station on 0845 6060606 or Crimestoppers anonymously on 0800 555 111.