Ronneberg's daring operation was given the Hollywood treatment in 1965 in the film "The Heroes of Telemark" starring Kirk Douglas.

"Ronneberg is probably the last of the best known resistance fighters to pass away," Norway's Prime Minister Erna Solberg told the NTB news agency.

Ronneberg trained with the Norwegian resistance in Britain and in February 1943 led a six-man team on a secret mission called Operation Gunnerside.

They sabotaged a plant in southern Norway that produced heavy water, a component in early nuclear energy research, putting a halt to the Nazis' nuclear weapon ambitions.

Situated near the city of Rjukan, the Vemork plant at the time was the only one in the world that produced significant quantities of heavy water.

After the war he turned to journalism and for a long time was reticent about his wartime experiences. Then in the 1970s he broke his silence, and became known for his involvement with young people to make them aware of the dangers of war.

"Those growing up today need to understand that we must always be ready to fight for peace and freedom," he said.