A gunman dressed in police uniform opened fire at an island retreat attended by the youth wing of Norway's ruling political party yesterday, killing at least 85 people.
The 32-year-old suspect is said to be a Christian fundamentalist with links to right-wing groups.
The death toll may grow further as a number of people remain missing. Teenagers at the lakeside camp fled screaming in panic, many leaping into the water to save themselves, when the assailant began spraying them with gunfire, witnesses said.
"I just saw people jumping into the water, about 50 people swimming towards the shore. People were crying, shaking, they were terrified," said Anita Lien (42) who lives by Tyrifjord lake, a few hundred metres (yards) from Utoeya.
"They were so young, between 14 and 19 years old."
Survivor Jorgen Benone said: "It was total chaos...I think several 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 metres away from me. I thought 'I'm terrified for my life', I thought of all the people I love.
"I saw some boats but I wasn't sure if I could trust them. I didn't know who I could trust any more."
"We had all gathered in the main house to talk about what had happened in Oslo. Suddenly we heard shots. First we thought it was nonsense. Then everyone started running," one survivor, a 16-year-old called Hana, told Norway's Aftenposten.
"I saw a policeman stand there with earplugs. He said 'I'd like to gather everyone'. Then he ran in and started shooting at people. We ran down towards the beach and began to swim."
Hana said the gunman fired at people in the water.
Many sought shelter in buildings as shots echoed across the island that was hosting the annual camp for the youth wing of the Labour Party, the dominant force in politics since World War Two. Others fled into the woods or tried to swim to safety.
"I saw he had a handgun," Thorbjoern Vereive (22) said.
"Some people said he also had something that looked like a rifle." "When I swam out into the water he shot all my friends. He shot them when they were running away. I hid in a cave and had to lie in the water. There were people hiding in the cave and he tried to lure people out by saying, 'It's safe, come out.'"
"He picked them out, one by one. He was mostly silent. It looked like it didn't bother him." "He tried to shoot me and I saw the bullet pass right next to me. I thought I was going to die."
Another youth, Dana Barzingi, described the massacre to state broadcaster NRK. "It was a bloodbath. There was nowhere to flee, only the water, and when people tried to swim away he just shot them." "He kept coming," said Barzingi.
"He went around and around pretending to be a rescue worker and said people should come to get help. Then he shot them."
Edvard Foernes (16) was taking part in the annual youth event for the first time, said the gunman shouted "Come out and play with me! Don't be shy."
"I was in my tent when the firing started. I thought it was fireworks. Somebody was screaming, 'Get the hell away!' and I thought they were joking. But then I saw people dying," he said.
"There were two people in a ditch. They said, 'Please don't shoot me,' and then he shot them like dogs."
He fled to the lake and plunged in.
"The attacker was 10 to 15 metres away from me and was aiming at me in the water." He said he had lost friends but didn't know how many.
One survivor estimated that the shooting went on for about an hour after starting at about 5.30pm. A police spokesman told reporters the shooting took place over a period of almost 90 minutes.
Boats searched for survivors into the night, searchlights sweeping the coast. Rescue helicopters flew overhead.
Prime minister Jens Stoltenberg said he knew many of the victims personally. "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 Utoeya is a national tragedy," he said of the small wooded holiday island where the gunman ran amok. "Not since World War Two has our country seen a greater crime."
Agencies