Iran on Thursday began the formal registration of presidential candidates ahead of a snap vote next month to replace the late Ebrahim Raisi who died in a helicopter crash.

"Candidate registration for the 14th presidential elections began at 8 am (0430 GMT)... at the interior ministry," the official IRNA news agency said.

Presidential hopefuls will have five days to register, IRNA added.

The elections were originally slated for 2025 but were brought forward following Raisi's unexpected death on May 19.

Raisi and seven members of his entourage, including foreign minister Hossein Amir-Abdollahian, were killed when their aircraft came down on a fog-shrouded mountainside in northern Iran.

The Islamic republic's supreme leader, Ayatollah Ali Khamenei, has since assigned vice president Mohammad Mokhber, 68, as caretaker president in accordance with the constitution.

On Thursday, state TV reported that "around 30 people" came forward to submit applications for candidacy, but "none of them met the basic conditions for qualification".

An AFP correspondent later saw former reformist lawmaker Mostafa Kavakebian and incumbent conservative parliamentarian Mohammadreza Sabaghian submitting their applications at the ministry.

Later, state TV showed former deputy foreign minister and nuclear negotiator Saeed Jalili, known for his inflexible negotiating stance, registering his candidacy.

The ultraconservative Jalili, 58, vehemently denounced a 2015 nuclear deal with global powers saying it "violated the red lines" of the Islamic republic by accepting "unusual inspections" of nuclear sites.

During the 2021 elections, he withdrew from the presidential race and supported Raisi's bid.

Candidates must be between the ages of 40 and 75 and have at least a master's degree, according to Iran's electoral law.

As in previous election cycles, the main candidates representing Iran's leading political camps are expected to submit their applications closer to the end of the registration process.

A final list of candidates will be announced on June 11 by the Guardian Council, a 12-member body of jurists whose members are either appointed or approved by the supreme leader.

The body disqualified multiple reformist and moderate figures ahead of the 2021 presidential elections which brought the ultraconservative Raisi to power.

Those elections had a record low turnout for a presidential poll, at just 48.8 percent.

The June vote will be held during a turbulent time, as the Gaza war rages between Iran's arch-foe Israel and Tehran-backed Palestinian militant group Hamas, and amid continued diplomatic tensions over Iran's nuclear programme.