Prayers for the innocent... justice for the perpetrators... here's a site with up to the minute updates (all times local Oslo time I believe):
6.12pm: NRK is reporting that one person has been arrested on the island of Utoya, where the shooting took place.
6.09pm: NRK is reporting that an unknown group called "Helpers of the Global Jihad" have posted a message that this is only the beginning of the reaction to Norwegian periodicals publishing the Muhammed cartoons, according to Andrew Boyle, a journalist in Norway.
6.01pm: John Magnus, chief foreign correspondent of Oslo's VG newspaper, told the Guardian he was sitting at his desk when the massive explosion in central Oslo today blew him off his chair.
It was 3.26 in the afternoon. The whole building was shaking. It was dancing. There was glass flying through the newsroom. I was on the far side of the building from where the prime minister's office is. The entire glass front of our building has been blown out ...
I saw people screaming and covered in blood. There were at least four people I saw who looked lifeless with their faces covered. We've had it confirmed that two people are dead but there are other locations that the emergency services have not reached yet.
Alyssa Nilsen told the Guardian: "My entire building was shaking ....People are lying across the street everywhere, I've seen people hanging out of the windows."
The Guardian has a gallery of today's tragic events.
5.48pm: In central Oslo, the train station has been evacuated as well as the headquarters of broadcaster TV2 because of suspicious packages.
5.47pm: Anti-terrorism police are being sent to Utoya where the Labour party youth camp has come under fire, the BBC is reporting. NRK says five people have been injured.
Andrew Boyle, a journalist in Norway, has sent me the following:
There are 700 people on the island camp. At 5.20 pm ambulance personel were told not to proceed out to the island because there was still shooting there. One Labour youth member tweeted: "We are sitting down by the beach. A man is shotting clothed in a police uniform. Help us! When are the police coming to help us!"
Police stormtroopers are about to land on Utoya island from helicopters. Shooting still going on. Eyewitness describes shooting from his position on the mainland: "There is a little war going on out there"
5.40pm: Police have confirmed the shooting incident, reports Reuters.
The news agency also quotes senior police officer, Thor Langli, saying the explosion that hit government buildings "may have been a car bomb".
Horrible stuff... and the death count is sure to rise.