Two people were killed and several others were seriously wounded in a shooting in central Oslo, Norwegian police said.
A suspect had been arrested, police said on Twitter after reporting a shooting at a nightclub.
The incident occurred near the London Pub gay club in the center of the Norwegian capital, according to media reports.
"Two people are confirmed dead after the shooting. There are several serious injuries," police said.
"In all, ten people are receiving treatment from health personnel. Three people are seriously injured," Tore Barstad, head of police operations, was quoted as saying by NRK radio.
Oslo University Hospital had received six injured people, whose condition was unknown, a hospital spokeswoman told TV2.
NRK reported there were three crime scenes but it was not clear if they were three different locations.
After the deadly overnight shooting, the Pride March that was due to take place the following afternoon has been called off.
"All events linked to Oslo Pride have been canceled" following "clear" recommendations by police, the organizers of the march wrote on Facebook. Police said earlier they were investigating the shootings as a "terrorist attack."