Riot police and security forces clashed with demonstrators in Tehran and dozens of cities across Iran on Saturday, Iranian news agencies and social media said, as protests against a rise in gasoline prices turned political. The reports said demonstrators chanted anti-government slogans around the country, a day after the government increased the price of regular gasoline to 15,000 rials ($0.13 cents) a litre from 10,000 rials and rationed it. Videos posted on social media from inside Iran showed protesters setting fire to buildings and clashing with riot police.