BBC News with Marion Marshall

Norway is

reeling from

two attacks in a number of hours, in which many people have been killed. The worse incident seemed to have been at a gathering of young people on an island northwest of Oslo. At least 10 people have been killed there. Bjoern Erik Sem-Jacobsen is the local acting chief of police.

"This afternoon, one person dressed like a police officer entered the island and said he was going to have control, and shortly

afterwards

he started the shooting. It's very likely to think that this has a connection with what has happened in central Oslo. People have been swimming ashore and hiding, and that is a critical, chaotic situation right now."

Police said later that they'd arrested one person in connection with the shootings. Earlier, an explosion in the centre of the Norwegian capital Oslo killed seven people and injured a number of others. Police said the blast was caused by a bomb, which ripped through government buildings, including the prime minister's office and Norway's biggest tabloid newspaper, but they said the prime minister was safe. Ingunn Andersen from the Norwegian broadcaster NRK was near the scene of the blast.

"All the buildings surrounding the main building were totally ruined, and glasses were all over streets, and there were people lying there, bleeding and chaos."

The Prime Minister Jens Stoltenberg said it wasn't clear who was behind the blast.