COPENHAGEN, Denmark — Norway on Monday mourned World War II saboteur Joachim Roenneberg, 99, who headed a five-man team that blew up a plant producing heavy water, depriving Nazi Germany of a key ingredient it could have used to make nuclear weapons.

Prime Minister Erna Solberg: Roenneberg was “one of our finest resistance fighters” whose “courage contributed to what has been referred to as the most successful sabotage campaign” in Norway.