A big explosion has hit government buildings in central Oslo on Friday.

The explosion damaged Prime Minister Jens Stoltenberg's office, causing most of his office windows to break. At least eight people were hurt or injured and at least one person was killed, according to the local media NRK.

According to eyewitnesses, buses were taking injured people out of the area.

The cause of the explosion is not known yet and police and fire officials have not commented on the incident.

All roads entering the city center have been closed, reported NRK, and security officials evacuated people from the location in anticipation of another possible explosion.