A massive bombing attack has hit government buildings in central Oslo on Friday.
At least seven people were killed and more than ten people were seriously injured by the explosion.
The blast broke most windows on the 17-story building housing Prime Minister Jens Stoltenberg's office. The nearby oil ministry building was also set ablaze by the bomb.
All roads entering the city center have been closed, reported Norwegian media NRK, and security officials evacuated people from the location in anticipation of another possible explosion.
A U.S. official said it was too soon to tell whether or not it was a terrorist attack. Terrorism is always a concern in Europe because of the continuous threat from al-Qaeda and possibly agents of Libyan strongman Muammar Gaddafi.
Rescue officials tend to a wounded man after a powerful explosion rocked central Oslo
Reuters
Rescue officials tend to a wounded man after a powerful explosion rocked central Oslo July 22, 2011. A huge explosion damaged government buildings in central Oslo on Friday including Prime Minister Jens Stoltenberg's office, injuring several people, a Reuters witness said. 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.
Reuters
Smoke billows from a 17-storey government building after a powerful explosion rocked central Oslo July 22, 2011. A huge explosion damaged government buildings in central Oslo on Friday including Prime Minister Jens Stoltenberg's office, injuring several people, a Reuters witness said. 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.
Reuters
Broken windows of a government building are seen after a powerful explosion rocked central Oslo July 22, 2011. A huge explosion damaged government buildings in central Oslo on Friday including Prime Minister Jens Stoltenberg's office, injuring several people, a Reuters witness said. 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.
Reuters
A rescue worker works at the site of a powerful explosion that rocked central Oslo July 22, 2011. A huge explosion damaged government buildings in central Oslo on Friday including Prime Minister Jens Stoltenberg's office, injuring several people, a Reuters witness said. 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.
Reuters
Rescue workers work at the site of a powerful explosion rocked central Oslo July 22, 2011. A huge explosion damaged government buildings in central Oslo on Friday including Prime Minister Jens Stoltenberg's office, injuring several people, a Reuters witness said. 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.
Reuters
Rescue workers work at the scene of a powerful explosion that rocked central Oslo July 22, 2011. A huge explosion damaged government buildings in central Oslo on Friday including Prime Minister Jens Stoltenberg's office, injuring several people, a Reuters witness said. 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.
Reuters