Amnesty International has called on Iranian authorities to "immediately end the arbitrary detention" of opposition figures Mehdi Karrubi and Mir Hossein Musavi and his wife, Zahra Rahnavard.
The human rights group issued the call in a statement on the third anniversary of the house arrest of the three figures.
It said they have been held without charge or trial for three years, with no possibility to challenge the lawfulness of their detention.
Amnesty said it was concerned about the health conditions of the three figures, all of whom are elderly and suffering from physical ailments.
Karrubi and Musavi ran in Iran's disputed 2009 presidential election, in which former President Mahmud Ahmadinejad was declared the winner.
They have been held under house arrest since February 2011 when they called for demonstrations in support of Arab Spring uprisings.
Based on reporting by RFE/RL
