Six leading human rights organizations have called on Iran to the end the "arbitrary" house arrest of opposition leaders Mir Hossein Mousavi and Mehdi Karroubi, who have been cut off from the outside world for nearly two years without being put on trial, The Guardian reports.

"For two years now Iranian officials have stripped these opposition figures of their most basic rights without any legal justification or any effective means of remedy," the Iranian Nobel peace prize laureate, Shirin Ebadi, said in a joint appeal signed by Amnesty International, Human Rights Watch, International Campaign for Human Rights in Iran, International Federation for Human Rights, League for the Defence of Human Rights in Iran, and Reporters Without Borders.

"They and their families should not have to endure even one more day under these wholly unjustifiable and abusive conditions," she said.

In mid-February 2011, following calls for street protests in solidarity with the pro-democracy movements in Egypt and Tunisia, dubbed the Arab spring, Iranian authorities placed Mousavi and Karroubi, along with their wives, Zahra Rahnavard and Fatemeh Karroubi, under house arrest.

Security forces initially blocked access to the houses of each couple in Tehran and did not allow them to leave, or their family members to enter the premises. Within a few weeks, the authorities who had surrounded the area entered the residences, ransacking rooms and confiscating documents, limiting the movements of the opposition leaders in an unprecedented fashion. Since then the authorities have released Fatemeh Karroubi from house arrest but increased the restrictions on the remaining three.

Earlier this week security officials in Iran picked up two daughters of Mousavi, Zahra and Narges, and one of Karroubi's sons, Hossein, from their houses in Tehran and questioned them for several hours before releasing them. They were apparently under pressure for speaking out about the plight of their parents.