In a series of haunting images to emerge from the tragedy, Breivik is seen dressed in the dark police uniform that won his victims’ trust, brandishing a weapon as lifeless bodies float in the shallows.

One disturbing photograph, published on our front page, shows a man waist-deep in the water, his hands aloft, apparently pleading for his life. It is not known whether he survived.

The bloodbath on the tiny island of Utoya has stunned Norway. Police last night said up to 98 people could have died, and added that they were planning to send an unmanned submarine to search Lake Tyrifjord.

Breivik, 32, has been charged over the massacre – and over the bombing in the government district of Oslo hours earlier which killed seven people.

Yesterday, survivors described the full horror of how the killer went on his deadly rampage, killing teenagers aged 14 to 19 at the youth camp.

They told in chilling detail how the gunman mowed down victims with a machine gun before clinically shooting them in the head with a shotgun. He also shot from the shore at terrified youngsters who had dived into the lake in a desperate attempt to escape.

One survivor told last night how he escaped by playing dead and hiding under victims’ bodies as the gunman opened fire.

As Breivik fired round upon round – many aimed at people’s backs as they ran away – eyewitnesses said the killer screamed: ‘You all must die.’ One unidentified teenage girl said the killer gathered his victims around before opening fire. She said: ‘He just said, “Come and be together.” Then people went up to him and he just shot them.’ Last night, a police source said Breivik, a 6ft blond Norwegian, was a Right-wing extremist who had posted anti-Muslim views on Christian fundamentalist websites.

Ruling out any terrorist motive, the police official said: ‘This seems like a madman’s work.’ Utoya was hosting an annual summer camp for the youth wing of Norway’s ruling Leftwing Labour Party, and the killer is believed to have tricked his way on to the island with a fake ID.

He was dressed as an anti-terrorist policeman and, according to some reports, initially told people he was there because of the earlier bomb on the mainland.

After Breivik had been taken for questioning, a government official revealed they were searching for unexploded devices on the island.

At least one such device was subsequently found, although it is not known whether Breivik planted it in advance or had brought it with him on the ferry on Friday. Police were disarming the device last night.

Stories also emerged yesterday of how holidaymakers and locals with boats braved the gunman’s fire to undertake a Dunkirkstyle operation to ferry survivors and wounded victims to safety on the nearby island of Storoya. Other survivors swam to safety to caves or hid behind walls, rocks and trees.

Red Cross worker Ståle Wig said: ‘It is a tough time for everyone and there are some really tragic stories emerging.

‘One group of six friends were sprinting away together through the forest as he chased them. After he had been chasing them for a while, they came to a crossroads and three went left and three went right.

‘In that moment they knew that some would survive and others wouldn’t. The killer chose to go left and the others heard the gunshots as he shot their friends. All those who went left died, those who went right lived.’ Adrian Pracon, who was working in an information booth on the island, spoke of how the gunman appeared to spare his life after he screamed: ‘No please, don’t do it.’ Mr Pracon then hid behind the bodies of those who had been shot and were playing dead. He recalled how he could ‘feel the killer’s breath, feel his boots and feel the warmth of the barrel’. He added: ‘I was perhaps seven feet away from him when he shouted that he would kill everyone, and everyone would die. People were falling dead right in front of me. I ran through the campus to the tent area. I saw the gunman – two people started to talk to him and two seconds later they were both shot. He was wearing a black uniform with red edges. He looked like a Nazi.

‘The gunman was very sure, very calm and controlled. He looked like he knew what he was doing. He screamed at us, “You all must die.”

‘We all started to run down to the water, people had already undressed and started swimming. I thought I didn’t have enough time to take off my clothes, so I started swimming in the rain in my clothes and big boots. I went for about 150 yards but the lake is about 900 yards long. I realised I wouldn’t make it so I turned back.

‘I saw him standing ten yards from me, shooting at the people who were swimming. He aimed the machine gun at me and I screamed at him, “No please no, don’t do it.”

‘I don’t know if he listened, but he spared me. He came back an hour later. I was with other survivors and we were lying down and hiding behind the trees and rocks. We were freezing in our wet clothes.

‘The shouting started again and people were falling on top of me, on my legs and falling into the water – that’s when many people died. I just had to shield myself behind them, praying he wouldn’t see me. Then he came closer, but I didn’t move and that is what saved my life.’ Erik Kusetgjerde, an 18-year-old Labour Party youth member, said the gunman ‘would tell people to come over, saying, “It’s OK, you’re safe, we’re coming to help you”‘. He added: ‘I saw about 20 people come towards him – and he shot them at close range.’ Survivor Dana Berzingi, 21, confirmed that the fake policeman ordered people to come closer, then pulled weapons and ammunition from a bag and started shooting.

He said that after shooting the victims with one gun, the gunman shot them again in the head with a shotgun.

Norwegian youth leader Lisa Marie Husby told how the gunman chased after her as she and 60 others fled to a nearby log cabin where she hid under a bed. They locked the doors and put mattresses in front of the window.

She said: ‘We ran to a cabin in the forest and he was running behind us. We got in the cabin and locked the door. I hid under the bed. It was quiet for 15 minutes and then he was trying to get into the cabin where we were hiding.

‘He shot through the door and the most terrifying part was him sticking a gun through the window. I hid under the bed until I knew I was safe.’ Emma, a youth leader who saw two men gunned down in front of her, initially thought someone was messing around when she heard the shots.

She ran towards the gunman because she thought he was a policeman who had come to help, but then saw a young man approach the ‘officer’ for assistance, only to be shot dead.

She and her boyfriend Erik ran into the water and hid in a cave ‘After an hour, we could actually smell the gunpowder and hear the shots above us,’ she said. ‘He was about ten feet away. He was trying to shoot people in the water as they tried to swim to the other side.’ Holidaymakers Lise Berit Aronsen and Ole Haugen, who picked up survivors in a boat, said the gunman had fired mercilessly at those trying to swim to safety. Ms Aronsen said: ‘We were told to find people in the water. The first we found were four children, two boys and two girls. They shouted for help.

‘They were powerless and could barely lift their arms. There were people crying for help everywhere. We saw children who hid in caves and on cliffs. They dared not come out until we said that the person who shot was taken. Then they wept freely.

‘One person had seen someone shot in the head, and we also saw several dead bodies in the water. Because we had such a small boat, we could not take many with us at a time. We were there early, so it was frustrating, but fortunately there were several boats eventually. It is absolutely unbelievable what has happened.’ Kasper Ilaug, 53, a computer programmer, used a friend’s boat to save some of the teenagers in three rescue missions. He saw several dead bodies, and teenagers crouching behind rocks and shrubs. ‘They were terrified,’ he said. ‘They waved to me. They were so grateful. These youngsters, they said, “Thank you, thank you, thank you.”‘ Anita Lien, 42, who lives by Tyrifjord lake, a few hundred yards from Utoya, said: ‘I saw people jumping into the water, about 50 people swimming towards the shore. People were crying, shaking, they were terrified. They were so young, between 14 and 19.’ Survivor Jorgen Benone said: ‘It was total chaos … I think several people lost their lives as they tried to get over to the mainland.

‘I saw people being shot. I tried to sit as quietly as possible. I was hiding behind some stones. I saw him once, just 20, 30 yards away from me. I thought, “I’m terrified for my life.” I thought of all the people I love.’ Yesterday, families gathered in a nearby hotel still hoping their loved ones are alive. The Norwegian royal family and prime minister Jens Stoltenberg also paid a visit.

Mr Stoltenberg said he knew many of the victims personally. ‘I know the young people and I know their parents. And what hurts more is that this place where I have been every summer since 1979, and where I have experienced joy, commitment and security, has been hit by brutal violence – a youth paradise has been transformed into a hell.

‘What happened at Utoya is a national tragedy. Not since World War Two has our country seen a greater crime.’ David Cameron condemned the attacks as ‘horrific’, saying that the people of the UK would stand with the country in the ‘days of sorrow that lie ahead’.

The Queen sent a message to the King of Norway, which read: ‘I am deeply saddened and shocked by the tragic loss of life of so many people on the island of Utoya and in Oslo. Prince Philip joins me in extending our heartfelt sympathy to Your Majesty and the people of Norway. Our prayers and thoughts are with everyone who has been affected by the dreadful atrocity.’ US Secretary of State Hillary Clinton also condemned the attacks. ‘This tragedy strikes right at the heart of the soul of a peaceful people,’ she said.

Last night, as Norway mourned the victims of Western Europe’s deadliest day of terror since the 2004 Madrid train bombings killed 191 people, there were unconfirmed reports of a second killer on the loose.

Norwegian officials, however, insisted that Breivik, a senior Freemason who enjoys bodybuilding and violent films, had acted alone.

It emerged that Breivik – who owns a farm – bought six tons of fertiliser from a farm supply store on May 4. A spokeswoman for agricultural supply company Felleskjopet said: ‘It was a small, normal order for a standard agricultural producer.’