Former Iranian president Akbar Hashemi Rafsanjani, a moderate who survived for decades despite challenging his own elite, died on Sunday after suffering a heart attack.

Rafsanjani, who was 82, was a pivotal figure in the foundation of the Islamic republic in 1979, and served as president from 1989 to 1997.

"Despite the efforts of the doctors he died" at Shohadaa Hospital in northern Tehran, said Reza Soleimani, a speaker of the Expediency Council, Iran's main political arbitration body which Rafsanjani chaired.

The government announced three days' of mourning, making Tuesday a public holiday for his burial, according to the official IRNA news agency.

Heartfelt tributes poured in from Iran's leadership, including the all-powerful Ayatollah Ali Khamenei, despite the differences between the two.

"The loss of my companion of struggle, whose cooperation with me dated back 59 years, is difficult and overwhelming," the supreme leader said in a statement.

"The different opinions and interpretations at times in this long period could never entirely break up the friendship" between us, Khamenei added.

President Hassan Rouhani, who was reportedly at Rafsanjani's bedside in the hospital, also expressed his grief in a tweet.

"The soul of the great man of the revolution and politics, the symbol of resistance and perseverence, ascended to heaven," he wrote.

Rafsanjani's death is a huge loss for both reformists and moderates, as he stood as a pillar for the two camps.