A number of email accounts linked to members and employees of Norway's parliament have recently been hacked, officials at the legislature say.
"We consider this matter to be a very serious one," said Marianne Andreassen, parliament's secretary general.
She also heads the legislature's administration.
"We are analysing the situation to get an overall picture of the incident and the potential extent of damage," she added.
According to initial analysis, data has been downloaded from the hacked email accounts.
The statement said "a small number" of email accounts were hacked.
The parliament administration has filed a police complaint and the Norwegian security service PST have also been notified.
The PST said that, when it received the formal notification, it would review whether there were grounds to launch a probe.
It was not known who was responsible for the hack.