According to the International Campaign for Human Rights in Iran (ICHR), Mir Hossein Mousavi and Mehdi Karroubi
were moved, but it is not known exactly when.An "informed source" also told the ICHR that Mousavi and Karroubi's detention location is not a prison.
Meanwhile,
...back at the ranch...
the head of the Iranian parliament's National Security Commission has said that Mousavi and Karroubi were "escorted" by security forces.
Alaeddin Boroujerdi also denied they were under house arrest, and told Italian newspaper Il Manifesto that "they also committed certain illegal acts such as organising protests without a permit, and for this they may become subject to prosecution".
The two men had been reportedly nabbed secretly without being summoned or charged, and their contact with the outside world was effectively cut.
The ICHR added they received reports that the powerful Iranian Revolutionary Guard was responsible for their transfer.
Mousavi and Karroubi's reported detention comes after the country's former reformist president called on the authorities to release them.
Mohammad Khatami posed the question on his website on Saturday, as to why "people like Mr Mousavi and Mr Karroubi, and their wives, who have had a glorious past in the revolution and the Islamic republic, and who are loyal to the revolution and the Islamic republic, be sent to his room?"
"Such action pushes people who are against the regime and who don't care for Iran ... to manipulate the feelings of our youths."
He also told the country's holy mans and university professors that he "hopes that with the start of the Iranian New Year [March 20] we will see the end of the house arrest, the end of restrictions, the release of the prisoners and the creation of a safe and free climate ... in which the people's vote will be decisive".
'No longer present'
It was the first time Khatami had called for the release of Mousavi and Karroubi.
Karroubi, Mousavi and their wives were under house arrest and living in complete isolation, their homes under surveillance and cut off from the outside world, according to their websites.
However,
The infamous
However...
one of Karroubi's neighbours told the ICHR that security forces were no longer present on his street, further cementing the speculation that he was moved to another location.
"I am certain that they are no longer inside their home. All the windows are broken and nobody is home," the neighbour said.
Khatami's comments came after the websites of Mousavi and Karroubi, who are steadfastly opposed to
Mahmoud Short RoundAhmadinejad, the president, had posted calls for new protests on Tuesday to demand their release.
The call to demonstrate was posted on Kaleme.com and Sahamnews.org and issued by the Co-ordination Council of the Green Path of Hope, an umbrella group backing the two leaders.
"We invite everyone to protest on Tuesday... against the continued restrictions and house arrest imposed on the movement's leaders," the group said in a statement posted online.
It also said the protests would be held in key squares and streets of Tehran and provincial cities.
Clashes between demonstrators and security forces killed at least two people on February 14.
'Anti-revolutionary'
But a massive deployment of security forces thwarted another protest in Tehran on February 20.
Ali Akbar Hashemi Rafsanjani, a former president who had indirectly backed Mousavi in the 2009 elections, condemned the February 14 protests, state media reported on Saturday.
The protests, the first to be held since February last year, angered the authorities who accused Mousavi and Karroubi of treason, according to opposition websites.
Officials have also branded anyone who supports the two men as "anti-revolutionary".
Mousavi and Karroubi led a string of protests in Iran after Ahmadinejad's controversial re-election in June 2009, which they claim was rigged.
Khatami, once a prominent figure of Iran's holy manal government, who served two terms in office between 1997 and 2005, has turned into a vocal critic since Ahmadinejad's re-election.