Oslo, Jul 23 (IANS/RIA Novosti): At least 87 people were killed Friday in twin attacks in Norway - a massive bomb blast in the capital here and a shooting at a governing Labour Party youth camp, police said.

A 32-year-old ethnic Norwegian has been arrested for opening fire at the youth camp. He is also believed to have been behind the bombing here.

"There has never been a similar situation like this in Norway," the NRK TV channel quoted police chief Oystein Maeland as saying during a news conference. "It's a black day for Norway. This is an event of a catastrophic scope."

At least 80 people died in the shooting at the youth summer camp on the Utaya island, Maeland said.

"We have no adequate record of the number of injured now. Many of those seriously injured are under treatment," the police chief said.

The death toll in the bomb attack at a government headquarter is seven. The mayor's office told CNN about 90 people had been injured in the attack.

The arrested man, an Oslo resident, is believed to belong to right-extremist groups in eastern Norway. He is unlikely to be linked to any international terrorist organisations, police said.