Iran's judiciary said Tuesday that a court had upheld death sentences for three people linked to deadly protests last November sparked by a hike in petrol prices.

The sentences were "confirmed by the supreme court after the defendants and their attorneys appealed," spokesman Gholamhossein Esmaili said, quoted by the judiciary's Mizan Online website. Esmaili did not name the defendants, but said two were arrested during an "armed robbery".

Evidence had been found on their phones of them setting alight banks, buses and public buildings in November, he said. The demonstrations erupted on November 15 after authorities more than doubled fuel prices overnight, exacerbating economic hardships in the sanctions-hit country.

They rocked a handful of cities before spreading to at least 100 urban centres across the Islamic republic. Petrol pumps were torched, police stations attacked and shops looted, before security forces stepped in amid a near-total internet blackout. "They had filmed it all audaciously, and sent (the footage) to some foreign news agencies," Esmaili said in a video released by state television. "They themselves had provided the best evidence."

Esmaili noted that the final verdict could still change over "extraordinary proceedings", according to the video released by state TV. He pointed to a legal clause that could trigger a retrial if deemed necessary by the chief justice. Reformist Shargh newspaper on Saturday named the three as Amirhossein Moradi, 26 and working at a cellphone retailer, Said Tamjidi, a 28-year-old student and Mohammad Rajabi, also 26.

Iran has blamed last year's violence on "thugs" backed by its foes the United States, Israel and Saudi Arabia. It pointed the finger at exiled royalists and the People's Mujahedeen of Iran (MEK), an exiled former rebel group which it considers a "terrorist cult". A senior Iranian lawmaker said in June that 230 were killed and thousands injured during the protests.

Authorities had for months refused to provide casualty figures, rejecting tolls given by foreign media and human rights groups as "lies".

London-based rights group Amnesty International has put the number of deaths at 304, and a group of independent UN rights experts said in December that 400 including at least 12 children could have been killed, based on unconfirmed reports. The United States has claimed that more than 1,000 were killed in the violence.