The attack against Labour is being compared to the hack of the Democratic National Committee that American intelligence agencies said was carried out by Russia in an effort to influence the outcome of the US election.
According to TV2's report, Labour's parliamentary group was notified of the hack by the Norwegian Police Security Service (Politiets Sikkerhetstjeneste - PST).
Labour's leader, Jonas Gahr Store, has confirmed that the party's electronic communications may have been compromised.
“I can confirm that we are informed by PST that Labour's parliamentary group was subjected to an attempted digital attack by a group that PST ties to foreign intelligence,” Store's press spokeswoman Camilla Ryste told Nettavisen.
According to a report in Dagbladet, the same group that hacked the Democrats in the United States carried out the attack on Labour as well.
The hack allegedly took place last autumn and "a handful of other Norwegian targets" were subjected to similar attacks. In a warning to members of parliament, Labour's secretariat director, Hans Kristian Amundsen, urged caution when conveying information over email and SMS. In the notification, Amundsen referred to an "attempt at digital attacks by an operator PST ties to foreign intelligence". Russia is not named directly in the letter sent to parliament.
“Take into account that the content can go astray, as happened with the e-mails to the Democrats in the United States," wrote Amundsen.
What, if anything, the hackers were able to gain is unknown.
"We have no information that the penetration succeeded, but was also don't have proof that it failed. The Norwegian authorities are working to investigate this. We will be briefed on the results," the warning letter stated.
Earlier this week, PST warned in its threat assessment that Russian intelligence poses a significant threat to Norway.
“Intelligence pressure from foreign states, especially from the Russian side, has been high and stable over the years. The reason why we increase [the risk] now is that there is a tougher security situation. This means that the intelligence activities of Russia in particular have the potential to be more dangerous now than before,” PST Chief Benedicte Bjørnland said.
On Thursday, the Russian Embassy in Norway sent an email to broadcaster NRK accusing the Norweigian intelligence service of being anti-Russian and “striving persistently to achieve a return to the times of the Cold War”. PST declined to comment on the embassy's statement.