TEHRAN - The son of an adviser to a defeated Iranian presidential candidate died after being beaten in jail, a semi-official news agency reported on Monday, citing a report from the coroner's office.

A reformist website last month said the son of Abdolhossein Ruholamini, who advised conservative Mohsen Rezaie in the disputed June presidential election, was killed in a Tehran prison after being detained in post-vote unrest.

Officials have said Mohsen Ruholamini died of meningitis. He was held in Tehran's Kahrizak jail, where many opposition protesters arrested after the disputed election were taken.

The Mehr news agency, citing an informed source, said the coroner's office, had submitted a report on the case to the legal authorities.

According to that report, the main causes of his death were physical stress, frequent beatings and hitting a solid object on his head, Mehr quoted its source as saying, adding he died while being transferred to a hospital.

Mehr did not give further detail and there was no immediate comment from the authorities.

In a meeting on Sunday with a group of academics including Abdolhossein Ruholamini, Supreme Leader Ayatollah Ali Khamenei said people responsible for crimes would face legal action.

All those who suffered from the recent events should know that the system is not intending to have an attitude of ignorance or forgiveness toward those who did bad things or committed crimes, said Iran's highest authority, who last month ordered the closure of the Kahrizak detention center.

New judiciary chief Ayatollah Sadeq Larijani has formed a committee to probe post-election events, including allegations that some imprisoned protesters were raped and abused.

Rights groups say thousands of people, including senior pro-reform activists, journalists, academics and lawyers, were arrested after the election. Many of them remain in jail.

Defeated moderate candidates Mirhossein Mousavi and Mehdi Karoubi say the poll was rigged in favor of President Mahmoud Ahmadinejad, a charge authorities deny. Rezaie came third.

Hardliners' have rejected as baseless Karoubi's allegation that some detainees, both men and women, were raped and abused.

But both parliament and the judiciary have now agreed to look into the matter, and the ILNA news agency said MPs involved in the inquiry had met with Larijani on Monday.

Ayatollah Larijani stressed that people's civil rights should be respected, said Kazem Jalali, a spokesman of a parliament committee investigating post-election events.

The vote and its turbulent aftermath have plunged Iran into its biggest internal crisis since the 1979 Islamic revolution and has exposed deepening divisions in its ruling elite.

Officials say at least 26 people died in the unrest, but opposition leaders have put the death toll at 69. Moderates and the authorities blame each other for the bloodshed.

(Reporting by Reza Derakhshi; writing by Fredrik Dahl; editing by Jon Boyle)