Iran’s hard-line former leader Mahmoud Ahmadinejad has registered as a possible candidate for the presidential election, seeking to regain the country’s top political position after a helicopter crash killed President Ebrahim Raissi.

The populist former leader’s registration puts pressure on Supreme Leader Ayatollah Ali Khamenei. In office, Mr Ahmadinejad openly challenged the 85-year-old cleric, and his attempt to run in 2021 was barred by the authorities.

The firebrand, Holocaust-questioning politician’s return comes at a time of heightened tensions between Iran and the West over Tehran’s rapidly advancing nuclear programme, its arming of Russia in its war on Ukraine, and its wide-reaching crackdowns on dissent.

Associated Press journalists in Tehran saw Mr Ahmadinejad arrive at the Interior Ministry and begin the registration process. Before his arrival, his supporters chanted and waved Iranian flags.

He descended the stairs at the ministry, showing his passport as is custom to dozens of photographers and video journalists on hand for the registration process.

As a woman processed his candidacy, he sat, turned to the journalists, nodding and smiling for the cameras. He was expected to give remarks after concluding his registration.

An election is planned on June 28 to replace Ayatollah Khamenei’s hard-line protege, President Ebrahim Raisi, who died in a helicopter crash in May along with seven other people.

Former parliament speaker Ali Larijani, a conservative with strong ties to Iran’s former relatively moderate president Hassan Rouhani, has already registered, as has former Iranian Central Bank chief Abdolnasser Hemmati, who also ran in 2021.

Who else will seek to run remains in question.

The country’s acting president, Mohammad Mokhber, previously a behind-the-scenes bureaucrat, could be the front-runner because he has already been seen meeting Ayatollah Khamenei.

Also discussed as a possible aspirant is former reformist president Mohammad Khatami, but, as with Mr Ahmadinejad, whether he would be allowed to run is another question.

The five-day registration period will close on Tuesday, and the Guardian Council is expected to issue its final list of candidates within 10 days. That will allow for a shortened two-week campaign before the vote in late June.

Mr Ahmadinejad previously served two four-year terms from 2005 to 2013. Under Iranian law, he became eligible to run again after four years out of office, but he remains a polarising figure even among fellow hard-liners.

His disputed re-election in 2009 sparked massive “Green Movement” protests and a sweeping crackdown in which thousands of people were detained and dozens were killed.

Abroad, he became a caricature of Western perceptions of the Islamic Republic’s worst attribute, questioning the Holocaust, insisting Iran had no gay or lesbian citizens, and hinting Iran could build a nuclear weapon if it chose to do so.

But he remains popular among the poor for his populist efforts and home-building programmes. Since leaving office, he has raised his profile via social media and written widely publicized letters to world leaders.

He has also criticised government corruption, though his own administration faced corruption allegations and two of his former vice presidents were jailed.

Ayatollah Khamenei warned Mr Ahmadinejad in 2017 that standing for office again would be a “polarised situation” which would be “harmful for the country”.

He said nothing during Mr Ahmadinejad’s 2021 attempt, when his candidacy was rejected by the 12-member Guardian Council, a panel of clerics and jurists ultimately overseen by Ayatollah Khamenei. That panel has never accepted a woman or anyone calling for radical change to the country’s governance.

The panel could reject Mr Ahmadinejad again. However, the race to replace Mr Raisi has yet to draw a candidate with clear, overwhelming support from Ayatollah Khamenei.