The survivors were pulled out shivering and bleeding from the water and picked up from hiding places in the bushes and behind rocks around the island's shoreline. And when darkness fell the bodies were hauled out by searchlight.

Local residents in a flotilla of little motorboats and fishing dinghies, knowing that a maniacal gunman was in the midst of a killing spree, bravely sailed out to rescue the dozens of terrified youngsters trapped on the tiny island of Utøya on Friday night.

Some youngsters were shot dead in the lake as they tried to swim to safety. Others who played dead were killed where they lay by the meticulous killer who checked his victims for signs of life before moving on, roaming the island and shooting everyone he could find. Edvard Fornes, 16, said the gunman told the youths: "Don't be shy," and, "Come and play with me", before executing them. "There were two kids hiding in a ditch," said Fornes, "saying: 'Please, please don't shoot us', and he shot them."

The killer began just after 5pm; it was two hours before 32-year-old Anders Behring Breivik, wearing the uniform of a police officer and protective earplugs against his own deafening gunshots, apparently ran out of ammunition and was arrested by police Swat teams sent from Oslo.

"We saw bodies in the water and children who hid in caves and on cliffs, they dared not come out until we said the gunman was taken, then they came crawling out weeping and screaming," said Lise Berit Aronsen, who took her boat out after hearing of the shootings on the radio. "It was horrible to see children in that state."

As Norway heard the death toll from Friday's two attacks rise from first two, then seven, then 10, deputy police chief Sveinung Sponhelm warned that there would be more. "This is the feedback from the island," he said.

In the early hours of Saturday morning it leaped to 80, even as survivors were still being picked up and the injured being taken to hospital. By dawn it was clear that 92 people had died in the violence, 85 on the island and seven in the fertiliser bomb that had ripped through the Oslo government building just before 3.26pm, an hour and a half before the island rampage, with hospital chiefs warning that there were so many badly hurt the toll could yet rise again. Explosives have been recovered from a car, thought to have been left parked next to the Utøya ferry.

"We greeted him as we got off the ferry," said a student who was leaving Utøya just as Breivik, dressed as a police officer, was boarding the boat for the island. "We thought it was great how quickly the police had come to reassure us of our safety because we had heard of the bombing in Oslo."

Police believe the man they now have in custody is responsible for the most terrible day of carnage in the country's postwar history and that he first watched his bomb rip through the Oslo city centre before driving the 20 miles to catch a boat to Utøya.

There were about 600 people, mostly aged between 14 and 25, on the wooded island, just over a quarter of a mile long, for the annual summer camp of Norway's Labour party youth wing.

"It was about 5pm. We had heard about the bomb in Oslo and had been gathering to discuss it, because of course some people had families in Oslo and were worried," said Adrian Pracon, one of the camp organisers.

"This man came along and said he was from the police and told us he would help us and make sure that everyone was OK but that man, dressed as a policeman, was the shooter. He had a machine gun, but it wasn't set to automatic fire, it was on single shot. He wasn't shooting like crazy or to make panic, he was shooting to kill people, with single bullets." Pracon said Breivik appeared cool and calm but looked like someone from a "Nazi movie".

"He saw someone run into their tent and he just slowly went to the tent, opening it and shot the people in the tent. He had been very prepared for this. He said he would kill us all and everyone shall die."

Many people ran into the water, where they were picked off one by one or were pulled under the water by the weight of their clothes and boots, Pracon said. "I tried to call the police [on my mobile], but so did 200 others, so the system went down. I lay down and acted as if I were dead.

He approached, two metres away. He was kicking people to see if they were alive or dead. I could hear him breathe, I could feel the warmth from the machine gun. I heard a big boom and I couldn't hear anything in my left ear. I didn't think I was hit but it turned out I was shot quite badly. There were about 20 people dead just around me."

Pracon was shot in the shoulder, but is expected to recover.

Prableen Kaur, the Oslo deputy leader of AUF, the Labour party youth wing, was chatting with friends when she heard the first shots. "Everyone was texting all around me. I texted my mum and dad to say I loved them. My mum rang and was crying. I cannot describe the fear."

She said that the gunman shot into bodies all around her. "I thought: 'Now it's over. He's here. He takes me. Now I'm dying'. People screamed. I heard them being shot. Others jumped into the water. I played dead. I lay there for at least an hour on top of a dead body. A man in a boat came to us. His boat was so small that it was taking in water and we had to keep using a bucket to get it out. I was exhausted. We came to the land. We got blankets. I cried and a woman hugged me. It was so good. I wept aloud. A man lent me his phone. I called my dad, I just told him: 'I'm alive'.

"I'm still in shock. I have seen the corpses of my friends. Several of my friends are missing. I am glad that I live. I think of all the relatives. Lives lost. And the hell that is and was on the island. This summer's most beautiful fairytale is transformed into Norway's worst nightmare."

Yesterday Norway's prime minister, Jens Stoltenberg, flew in by helicopter to visit other survivors who had been taken to a hotel in the town of Sundvolden to be interviewed by police and reunited with families.

"I know the young people and I know their parents," he said. "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 Utøya is a national tragedy."

Because of what was unfolding in Oslo many of the people on Utøya were convinced that the gunshots were some kind of "sick joke".

Hana Barzingi was one of them. "I said to him 'What the hell are you doing?'" In the confusion she was able to throw herself into the lake, hiding between bodies. She was lying in the water for two hours before she heard the police helicopters above and knew help was on its way and was pulled from the water by two local men in a boat.

But even as rescue approached, many were too terrified to come out of hiding. Hana's brother Dana Barzingi, deputy chairman of Skedsmo AUF, was in a dining room with friends when the shooting started. "Some of my friends tried to talk to him, some people went to him and tried to talk to him, but they got shot immediately," he said.

Like many of the young people on the island, Niclas Tokerud, sent text messages to his family as he hid. "He sent me a text saying 'There's been gunshots. I am scared … But I am hiding and safe. I love you'," said his sister Nadia, a 25-year-old graphic designer in Hokksund, Norway.

Norway was in shock and grief. "This is a situation that affects us all. This is an event of catastrophic scale," said police director Oystein Maeland. "Like all Norwegians feel, I now have a sensation of shock that is hard to put into words."

The explosion in Oslo was being called "Destiny Time" by Norwegian papers. It had initially led many to leap to the conclusion that Islamist terrorism had reached the ordered streets of the Norwegian capital. But even as footage of the fluttering blinds on the shattered windows of the government buildings began to flash around the world, the home-grown terrorist was moving on to his next, even deadlier target, just 20 miles away.

It was then, before the news of an arrest broke, a clearly emotional Stoltenberg had said: "You shall not destroy us, you shall not destroy our democracy and commitment. We are a small but proud nation. No one should scare us or shoot us into silence. No one should scare us from being Norway."

On Saturday that sentiment was being picked up by defiant Norwegians.

Youth camp leader Eskil Pedersen said there was "no doubt" in his mind that the Labour party was the target of the attack on Utøya. He vowed there would be no surrender of ideals and promised that the summer camp would return to Utøya. "We meet terror and violence with more democracy and will continue to fight against intolerance," he said.