The seizure of the award, unprecedented in its 108-year history, caused outrage in Olso, where the Nobel Peace Committee is based.
The Norwegian Government summoned the Iranian envoy to protest, and the committee said that it would make a formal complaint.
"Such an act leaves us feeling shock and disbelief," said Jonas Gahr Store, the Norwegian Foreign Minister.
Geir Lundestad, secretary of the committee, said that Iran's action was unacceptable. "A laureate has never been treated like that. Even political dissidents such as [Andrei] Sakharov and [Lech] Walesa were better treated in their countries," he added, referring to the Russian dissident and the Polish trade union leader, both of whom won the prize while living in the Soviet bloc.