Iranian President Hassan Rouhani has justified the decision to increase fuel prices. However, responding to protests, he said that poor people will start receiving subsidies from Monday.
At least two people have been killed as a result of the protests and several others injured as they tried to enter an oil refinery.
The interior minister has warned security forces will act to restore calm if needed.
According to Iranian media, over 1,000 people have already been arrested.
Al Jazeera's Dorsa Jabbari reports from Tehran.
Mohammad Marandi, the Dean of the Faculty of World Studie at the University of Tehran talks to Al Jazeera.