Where are Iran opposition leaders Mousavi and Karroubi?

There are conflicting reports about the current whereabouts of Iran’s two most prominent opposition leaders, Mir Hossein Mousavi and Mehdi Karroubi.

Karroubi’s son told the BBC that his father and mother, who were already under house arrest, has been taken from their homes by state security officer, but he did not know where. Also, a website linked to Mousavi claims that Mousavi and Karroubi have been taken to the Heshmatiyeh jail in Tehran.
However, the Iranian government, according to Fars, the semi- official news agency, has denied these reports.

The two men [Mousavi and Karroubi] are currently in their homes and there have only been restrictions on their contacts, an unidentified state official said.

The confusion comes ahead of plans by opposition groups (as well as Mousavi and Karroubi) to stage a huge protest rally Tuesday, inspired by anti-government rallies in Tunisia and Egypt and elsewhere.
The government has warned people not to attend the rallies,

“Anyone who acts against the law will be dealt with,” Gholam Hossein Mohseni Ejeie, the Iranian prosecutor general, was quoted as saying on state television.

A previous demonstration on February 14 led to serious clashes, resulting in the arrest of about 1,500 people, according to opposition groups. Subsequent to this, a group of conservative Iranian MPs demanded that Mousavi and Karroubi be tried and executed.

Following the deadly clashes, Iranian MPs called for the two opposition leaders to be tried and executed. The Middle East in crisis: Iran arrests opposition leaders

The International Campaign for Human Rights in Iran has condemned the treatment of Mousavi and Karroubi and their wives.

The four prominent people have been disappeared; they are being held incommunicado in an unknown location, a severe breach of Iranian and international law, Aaron Rhodes, a spokesperson for the Campaign, said. Given the lynch mob-like calls for their execution by numerous Iranian politicians and clerics, there is reason to be deeply concerned for their safety and well being.