NESLANDET, Norway - Norwegian teenagers at a lakeside summer camp fled screaming in panic, many leaping into the water to save themselves, when an attacker dressed as a policeman began spraying them with gunfire.

Police said at least 10 of the youngsters, attending a camp run by the governing Labour Party, were killed in Friday's attack, shortly after a blast in the capital Oslo killed seven people in Western Europe's worst bombing since 2005.

"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 island, northwest of Oslo.

Survivor Jorgen Benone, who was on the island at the time, 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."

Gunman tricked his way on

Utoeya is an island about 500 metres long, clad with pine trees. Lien said the shooting sounded like automatic gunfire.

A camp guard, Simen Braenden Mortensen, said that the gunman had tricked his way onto the island by posing as a policeman driving a silver grey car.

"He gets out of the car and shows ID, says he's sent there to check security, that that is purely routine in connection with the terror attack (in Oslo)," Mortensen told the daily Verdens Gang.

"It all looks fine, and a boat is called and it carries him over to Utoeya. A few minutes passed, then we heard shots," he said.

Police said they had found undetonated explosives on the island. They said the gunman, whom they described as ethnic Norwegian, may also have been involved in planting the bomb in Oslo.

Early on Saturday, an ambulance left the lake area, with a body lying on a stretcher inside. Cars with distraught relatives were heading to a nearby hotel hoping to meet loved ones evacuated from the island.

Police and dogs were still searching the island and lake overnight from boats and helicopters, with ambulances on standby. Searchlights slowly swept the water in the dark.

Survivor Benone said he was finally picked up by a rescuer in a boat.

"I just jumped into the water and swam to the boat. I was crying, that's how happy I was. And I was so cold, ice cold.

"I'm just happy to be alive."