By Yeganeh Torbati
DUBAI (Reuters) - A former Iranian prosecutor linked to the deaths of anti-government protesters was arrested on Tuesday as a public showdown between President Mahmoud Ahmadinejad and his big political rival, Ali Larijani, gathers pace.
Tensions burst into the open on Sunday when parliament dismissed Ahmadinejad's labor minister for hiring the prosecutor, Saeed Mortazavi, and Ahmadinejad tried to protect the minister by taking the floor to hurl corruption allegations at the family of Larijani, the parliamentary speaker.
Ahmadinejad is fighting to remain relevant as his second and last term in office draws to a close. With parliament and Larijani, a possible candidate in June's presidential election, becoming more assertive, Supreme Leader Ayatollah Ali Khamenei has called for unity to little avail.
"The Tehran prosecutor announced on Monday night that Saeed Mortazavi has been arrested," read a one-line statement from the prosecutor's office, giving no reason for the arrest.
Mortazavi has played a central role in stamping out dissent since Ahmadinejad's disputed re-election in 2009, and has been described by Human Rights Watch as a "serial human rights abuser".
Before leaving Tehran's Mehrabad Airport for Cairo, Ahmadinejad struck a defiant tone, and said he would investigate the case on his return.
"THIS IS UGLY"
"The judiciary is not a special family organization," he told reporters, according to the state news agency IRNA. The head of Iran's judiciary is Sadeq Larijani, the speaker's brother.
"I don't know how it has happened that one person has committed an infraction, and another person is arrested," Ahmadinejad said. "Instead of going after the violator, they go after the person who has announced the violation, and this is very ugly."
Mortazavi was arrested as he was leaving his office on Monday, and taken to Evin prison, Fars news agency reported.
He had been suspended from his judicial post over the deaths by torture of three protesters in custody after the 2009 presidential election. The opposition said at the time that the election had been rigged in Ahmadinejad's favor, and huge protests were put down by force.
Fars said Mortazavi's arrest could be linked to his involvement in the prison deaths. Iran's judiciary said in January that a court would address the cases in March.
Analysts say the detention would not have been possible without Khamenei's consent.
"Mortazavi's arrest was part of the payback for the president's appearance in parliament," said a Western diplomat based in Tehran.
In his speech in parliament, Ahmadinejad played a tape that he said showed a meeting between Larijani's brother Fazel and the former Tehran prosecutor in which Fazel Larijani attempted to use his family's political status for financial gain.
"His meeting (appearance in parliament), along with the taped accusations, was seen as badly overstepping his rights," the diplomat said.
The president's political star has been on the wane since he fell out with parliament early in his second term and appeared to lose Khamenei's support.
Both Fazel and Ali Larijani denied the accusation of corruption. Ali Larijani, who represents the Shi'ite Muslim clerical center of Qom in parliament, accused the president of not observing "the basics of proper behavior".
Fazel Larijani said he would file a legal complaint against both Ahmadinejad and Mortazavi.
Labour Minister Abdolreza Sheikholeslami, who was dismissed by parliament on Sunday, defied the anger of lawmakers last year to appoint Mortazavi to head his social security office.
Dubbed by critics as "the butcher of the press", Mortazavi had a central role in shutting down reformist newspapers and arresting dozens of journalists.
Mortazavi was also involved in the case of Iranian-Canadian photographer Zahra Kazemi, who died in custody in 2003.
Yasmin Alem, a U.S.-based expert on Iran's electoral system, said Mortazavi's actions had imposed a "significant cost" on Iran's ruling system in the last 10 years.
"Over the last decade, his name has been closely linked to most, if not all, of Iran's human rights-related imbroglios," she said. "He's at the crux of a political fiasco that has brought all the regime's dark secrets to the surface."
(Editing by Marcus George and Kevin Liffey)