Two of Iran's main opposition leaders and their wives are said to be in grave danger after security forces apparently abducted them from their homes, where they were under house arrest.
The claim, by the International Campaign for Human Rights in Iran, indicates a serious escalation in the Iranian government's effort to silence the opposition movement that grew out of protests over the disputed presidential election in June 2009.
One of the missing politicians is Mir Hossein Mousavi, who ran for president in the 2009 election against the incumbent, Mahmoud Ahmadinejad. Mr Ahmadinejad was declared the winner despite widespread charges of irregularities in the voting. The other is Mahdi Karroubi, a former Speaker of the Iranian parliament, who also ran on a pro-reform platform in the election.
The two had been under house arrest since calling for a rally on 14 February in solidarity with the uprising in Egypt. Iranian security forces patrolled the streets in front of their houses and kept visitors and relatives from entering. Three demonstrators were killed in a harsh security crackdown on the two days of protests that coincided with popular revolts across the region against autocratic regimes.
In a stormy session of the Iranian parliament on 15 February, members clamoured for Mr Mousavi and Mr Karroubi to be put to death.
The New York-based human rights group said in a statement yesterday that a neighbour and a witness reported that the security guard at both men's houses was gone, and there was no sign that the politicians or their wives were still in their homes.
The group quoted an unnamed source as saying the two couples had been taken to a "safe house" in the Tehran area.
In the Iranian context, a safe house is often anything but, it said, a place where detainees are mistreated by Revolutionary Guard forces as a way to extract confessions without any judiciary oversight.
"The campaign finds it deeply disturbing that Mousavi and Karroubi have reportedly been removed to such a facility," the group's statement added.
Aaron Rhodes, a spokesman for the rights group, said the men's disappearance under these circumstances meant they were in danger. "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." A further call for the release of the two opposition leaders came yesterday from the former Iranian President Mohammad Khatami, but he did not refer to their apparent abduction.
Mr Khatami, also a reformist, has himself come under attack from hard-liners but remains popular in Iran since his presidency, which ran from from 1997 to 2005. A statement on hiswebsite yesterday quoted him as saying he hoped the opposition leaders would be released soon.
"Why should people like Mousavi and Karroubi, with their stellar background in the Revolution and the Islamic Republic and complete faith in the substance of the regime and the Revolution,,be under house arrest and subjected to such restrictions?" Mr Khatami said. He also hoped for "the creation of a safe and free climate".
Mr Karroubi's US-based spokesman was not available for comment.
In Iran, activists and opposition members have demanded that Mr Mousavi and Mr Karroubi be released, vowing to stage demonstrations every Tuesday until they are freed.