"The opposition movement is very much looking for martyrs so if this is true, it's for their own safety," an official said of the government's move to hide Mir Hossein Moussavi, Mehdi Karrubi and their wives, CNN reported Sunday.
The opposition movement, which favors political reform, "is always looking for an excuse to create something, so this [was done] to keep someone from doing something to them," the unidentified official said.
"Moussavi and Karrubi and their wives have been [made to disappear]. They are being held incommunicado in an unknown location, a severe breach of Iranian and international law," said Aaron Rhodes, a spokesman for the International Campaign for Human Rights in Iran.
"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."
Press TV of Tehran had broadcast a video this month of Iranian lawmakers chanting, "Moussavi, Karrubi ... execute them."
A "safe house" is a place for secretly holding high security detainees. Such locations are outside the purview of the judiciary or other monitoring systems. Iranian intelligence agencies are renowned for using such locations to extract confessions from detainees, CNN reported.
"Given the use of so-called safe houses to mistreat opponents of the government in the past, the campaign finds it deeply disturbing that Moussavi and Karrubi have reportedly been removed to such a facility," the human rights group said.