The cause of the blast was unknown but the tangled wreckage of a car was outside one building and the damage appeared consistent to witnesses with that from car bombs. Police and fire officials declined comment on the cause.
The blast blew out most windows on the 17-storey building housing Stoltenberg's office, as well as nearby ministries including the oil ministry, which was on fire.
Heavy debris littered the streets and a tall plume of brown smoke over the city centre.
A Reuters correspondent counted at least eight injured people. Norwegian news agency NTB said that Stoltenberg was safe in the blast, which happened around 3:30 p.m. (1330 GMT).
"It exploded, it must have been a bomb. People ran in panic. I counted at least 10 injured people," said Kjersti Vedun, who was leaving the area.
NATO member Norway has sometimes in the past been threatened by leaders of al Qaeda for its involvement in Afghanistan. It has also taken part the NATO bombing of Libya, where Muammar Qaddafi has threatened to strike back in Europe.
However, political violence is virtually unknown in the country.
David Lea, Western Europe analyst, at Control Risks said: "It's very difficult to tell what has happened. There certainly aren't any domestic Norwegian terrorist groups although there have been some al Qaeda-linked arrests from time to time.
"They are in Afghanistan and were involved in Libya, but it's far too soon to draw any conclusions."
COMMENTS (12)
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@Tahir: I didnt see how a freemason conservative nationalist norwegian who was shooting is related to Islam.
Gladio boys are back.
Killing of innocent people is wrong whether they are muslims or non..Dats wat our religion says.
I am sure none of the indian troll are going to post on this news item again!
Norway stopped bombing Libyan cities, this bombing is a way to get them back on the illegal Libyan war.
unfortunately Oslo has a huge pakistani population i really hope they were not involved. Also i dont know why we have to go to western nations illegally and seek asylum there and then hate them and bomb them.
That's sad. RIP.
I am sure the Root Cause Theorists will have a convincing explanation for the bomb blast in Norway.
Yet another blow to the Muslim credibility in the entire world. Tomorrow, Alqeada will take responsibility and the Muslims in Europe would brace for another wave of hatred that was somewhat thawed over the past couple of years.
God bless Muslims!
Terror charges against Mullah Krekar could be a cause.
http://www.bbc.co.uk/news/10554523
Back in 2010, 3 people were arrested over alleged planning of bombing targets in Oslo.
That should teach those cartoonists from another country, right?