At a press conference held at 3:30 am local time, Oystein Maeland police chief confirmed the death and said he could not guarantee that the number of deaths will not increase.
"This is a situation that affects us all," said Maeland, according to Norway's NRK national TV broadcasts.
The youths were attending a summer camp of the ruling Labour Party's youth. Prime Minister Jens Stoltenberg is scheduled to visit the camp on Saturday (23 / 7).
A man identified as 32-year-Anders Breivik Behring was arrested after the shooting and he allegedly responsible for both attacks.
Breivik arrived on the island wearing a police uniform and called a group in camp - and then shots aimed at them. Some young men tried to swim to escape from the island. Residents were told there has been a shooting and anyone who had a boat called upon to help rescue swimmers. NRK capture photos corpse on the beach.
Lise Berit Aronsen and Ole Haugen, a vacation near the island, turn their boats to search for survivors. They heard the call of four swimmers, two girls and two boys, and save them. "They're running out of energy," said the Norwegian newspaper VG Aronsen.
Prime Minister Jens Stoltenberg vows to "find the perpetrators"
"We will not allow them to destroy us and destroy our democracy. We are a small country but we are proud of," Stoltenberg said in the newspaper Aftenposten. The leaders of other countries, including President Obama and German Chancellor Angela Merkel condemned the attack.
Motives unclear, but the Norwegian media revealed that he is connected to an extremist group in the eastern part of the country. He regularly leave comments on the political forum Document.no Norway website.
Latest posting on his Twitter account, Breivik wrote "One person with belief is equal to the strength of 100,000 who have only interests."
NRK reported that Breivik has two weapons listed under his name, and owned his own company that buys and sells food ingredients.
"This is the biggest challenge for us after the war," said Kari Henriksen, a top Labour Party politician.
All of Norway's media use at least double the main page for their main report relating to the attack. (EpochTimes / sum)