Mousavi, who served as the prime minister of Iran from 1981 to 1989, was widely respected for his reformist agenda.

An architect by profession, Mousavi was the last PM of the Islamic Republic, and was hailed for his handling of the Iran-Iraq war and the country's economy.

Mousavi has promised to change the country's economic structure and end Iran's international isolation. His decision to contest the presidential election was welcomed by trade unions and grass-roots activists.