Iranian authorities have denied reports that senior opposition leaders Mir Hossein Mousavi and Mahdi Karroubi are being held in a prison in Tehran.
The men and their spouses were reportedly taken from their homes, where they had been on house arrest, and transferred to Heshmatieh Prison, according to the Human Rights House of Iran (RAHANA).
RAHANA reported the Mousavis' daughters have been unable to contact their parents.
Neighbors of the Karroubi family told SahamNews that eight vans parked near their home on Thursday evening left, along with a car, that had been parked in the building's garage.
Iranian authorities called the reports false but refused further comment on their whereabouts, calling the matter a "completely domestic" affair, The Associated Press reported.
"The internal issues of our country are completely domestic and no country is and will be allowed to interfere in the internal affairs of our country," Iranian Foreign Ministry spokesman Ramin Mehmanparast said. He added that "issues relating" to the two opposition leaders "will be dealt [with] in the framework of law by judicial authorities."
Meanwhile, Iran's semi-official ISNA news agency quoted chief prosecutor Gholam Hossein Mohseni Ejei saying the two opposition leaders had not been arrested.
News of the opposition leaders' detention came two weeks after anti-government protesters turned out by the hundreds of thousands in a show of support for the democratic uprisings in Egypt.
On Tuesday, Iranian security forces used tear gas and other riot control gear against resurgent anti-government protesters. Two demonstrators were killed, dozens injured and an unknown number arrested, according to Iran's state-run media. The government banned foreign media coverage.
Meanwhile, more than 220 Iranian parliamentarians have signed a statement demanding that Mousavi and Karroubi face the death penalty for organizing the demonstrations. Iranian television aired video of lawmakers chanting "Death to Mousavi, death to Karroubi."