Iranian authorities have issued an arrest warrant for the son of influential former President Akbar Hashemi Rafsanjani on charges of helping foment last year's postelection unrest, state radio reported Tuesday.

In the turmoil that swept Iran after the disputed June 2009 presidential election, the ruling establishment sought to contain the powerful Rafsanjani, who supported an opposition candidate and appeared to side with critics alleging vote fraud.

His son, Mahdi Hashemi, has been living in Britain since shortly after the election, and it appeared that authorities were targeting him primarily to deliver another warning to his father.

Since last year, judiciary officials and other hard-liners have been challenging Hashemi to return to Iran to answer accusations of encouraging anti-government violence. Hashemi, who has denied the charges, is not known to have had any key role in the opposition movement or the street protests.

The deputy head of Iran's judiciary, Ebrahim Raisi, said an arrest warrant has now been issued and he would be taken into custody upon his return to the country, according to Tuesday's radio report.

Earlier this week, Hashemi said in a letter to the judiciary that he would return only with guarantees that his trial would be "fair and preferably open." Raisi said it would be fair.

Mahmoud Ahmadinejad's re-election last year set off months of street protests by opposition activists claiming vote fraud. The anger quickly broadened to target Iran's ruling system.

Authorities responded with a massive crackdown and a mass trial of more than 100 activists and officials from previous pro-reform governments.

The moderate Rafsanjani was president from 1989-97. In last year's election, he supported opposition leader Mir Hossein Mousavi, who claimed he was robbed of victory through fraud.

The unrest was the biggest challenge to Iran's leaders since the 1979 revolution that toppled the U.S.-backed shah and brought hard-line clerics to power.

The ruling establishment came to see Rafsanjani as a serious threat, worrying that they had a dissenter within their ranks. There have been several attempts to sideline the former president, who is a powerful combination of elder statesman, super-wealthy tycoon and head of the only group empowered to remove Iran's supreme leader.

Besides accusing him of unspecified corruption, authorities have also gone after his children.

During the postelection protests, authorities briefly held Rafsanjani's daughter, Faezeh, a pro-reform former lawmaker who strongly backed Mousavi. The detention was widely interpreted as a warning to Rafsanjani to stay out of the turmoil.

(This version CORRECTS the spelling of the judiciary official's name).)