Former Iranian president Akbar Hashemi Rafsanjani died on Sunday at the age of 82, Elombah.com has learnt
Al Jazeera and other news agencies reports thyat Rafsanjani, who served as president from 1989 to 1997, was taken to hospital in the capital Tehran with heart problems, the ISNA and Fars news agencies reported.
He had been admitted to the Shohadaa Hospital in northern Tehran, one of his relatives, Hossein Marashi, was quoted as saying by the agencies.
Al Jazeera's Dosra Jabbari, reporting from Tehran, said Iranian officials described his death as a "huge loss" to the country.
"His death couldn't come at a worst time for the country because there are disputes between the current government and the judiciary and Rafsanjani was seen as a mediator," she said.
"He would advise on how to deal with such situations in the country. With the news of his death many people are in absolute shock."
Following the news of Rafsanjani's death, a crowd gathered outside the hospital in Tehran's Tajrish neighbourhood where he had been taken, according to residents.
Rafsanjani was an influential figure in Iran, and headed the Expediency Council, a body which is intended to resolve disputes between the parliament and the Guardian Council.
He was also a member of the Assembly of Experts, the clerical body that selects the supreme leader, Iran's most powerful figure.
Rafsanjani has been described as "a pillar of the Islamic revolution".
His pragmatic policies, economic liberalisation, better relations with the West and empowering Iran's elected bodies, appealed to many Iranians but was despised by hardliners.
His death is a big blow to moderates and reformists, depriving them of their most influential supporter in the Islamic establishment.
Since 2009 he and his family have faced criticism over their support for the opposition movement which lost that year's disputed election to former president Mahmoud Ahmadinejad.