COPENHAGEN, Denmark—Arne Treholt, the former Norwegian Foreign Ministry official who was convicted of spying for the Soviet Union in what became Norway’s biggest Cold War espionage scandal, has died, authorities said Monday. He was 80.

In 1985, Treholt was sentenced to 20 years for giving Norwegian and NATO defense plans along with sensitive political information to his Soviet handlers over a nine-year period. He was also convicted of carrying out less serious intelligence breaches for Iraq.

Treholt, who claimed he worked as a “business consultant,” confessed to meeting and taking money from people working for the KGB. However, he denied being a spy in several books he later wrote and made several unsuccessful bids to have a retrial in Norway.

He was pardoned in 1992 on health reasons and left Norway to live in Cyprus and in Moscow.

The Norwegian Foreign Ministry confirmed it was aware of his death but provided no further details. Aftenposten, one of Norway’s largest dailies, wrote Sunday that Treholt had died after a brief disease in Moscow. Aftenposten also said he was survived by a son and two grandchildren.