Norwegian intelligence revealed on Friday that the country's foreign ministry, defence ministry and other institutions have been targeted by hackers believed to have ties with Russian authorities.

The group suspected to be behind the cyberattack - APT 29, also known as Cozy Bear - has been previously been linked to the attack on the Democratic National Committee (DNC) during the US presidential election campaign last year.

"Nine different email accounts were targeted in an attempt at what is called spear phishing, in other words, malicious emails," Arne Christian Haugstoyl, an official with Norway's Policy Security Service (Politiets Sikkerhetstjeneste - PST), told Norway's TV2.

The security service no classified information was obtained in the cyberattack.

Norway's foreign ministry, army, the radiation protection agency, the parliamentary group of the Labour party, the PST and a school were targeted in the cyberattack.

Prime Minister Erna Solberg said the cyberattack is a "serious attack on our democratic institutions."

"We cannot assume that we are less vulnerable that other countries, so it is incredibly important that everyone take precautions to not open e-mails [when] you do not know the sender."

PST spokesman Martin Bernsen told the Associated Press that the intelligence agency was warned by a foreign agency earlier this year about "targeted attacks" on the security service, the Norwegian Labour Party, the military and multiple other government agencies. However, he declined to specify the foreign agency.

"The attacks had a signature that indicates those behind the hacking can be identified as APT29," Bernsen said. "They can be traced back to Russia."

Earlier this week, Labour leader Jonas Gahr Store confirmed that the party's parliamentary group was the victim of an attempted cyberattack in the second half of 2016.

"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," Labour spokeswoman Camilla Ryste told Nettavisen.

Labour's secretariat director Hans Kristian Amundsen warned members of parliament in a letter to practice caution when relaying information via email and SMS, Norwegian media outlet The Local reports. In the letter, Amundsen mentioned an "attempt at digital attacks by an operator PST ties to foreign intelligence."

"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," Amundsen wrote. "Take into account that the content can go astray, as happened with the e-mails to the Democrats in the United States."

Cozy Bear is suspected of infiltrating the DNC's computer system and having ties with the Russian Federal Security Service (FSB).

US intelligence agencies concluded that President Vladimir Putin ordered a complex, multi-faceted influence campaign that combined "covert intelligence operations - such as cyber activity - with overt efforts by Russian Government agencies, state-funded media, third-party intermediaries, and paid social media users or 'trolls.'"

The report said the campaign was designed to undermine American democracy, discredit Democratic candidate Hillary Clinton's campaign and bolster Donald Trump's chances of winning the presidency.

Moscow, however, has vehemently denied these claims.

In its annual threat assessment released this week, the PST warned that Russian intelligence does pose as a serious security threat to the country.

"Intelligence pressure from foreign states, especially from the Russian side, has been high and stable over the years," PST head PST Chief Benedicte Bjørnland said.

The Russian embassy in Oslo, however, called the report a "witch-hunt" that aims to scare the Norwegian public and return to the "times of the Cold War."