Iran's interior minister called on citizens to avoid "illegal gatherings" after two days of angry protests against the regime and an array of economic problems.

"We urge all those who receive these calls to protest not to participate in these illegal gatherings as they will create problems for themselves and other citizens," said Abdolrahman Rahmani Fazli, according to the semi-official ISNA news agency.

Read more: US condemns arrest of demonstrators in Iran

"People who want to hold a rally must file a request and the interior ministry and the provincial governor's office will review it," he added.

Protests began in second city Mashhad on Thursday before spreading to several other cities into Friday.

Initially focused on high living costs, they quickly turned against the Islamic regime as a whole with people chanting "Death to the dictator" and "Free political prisoners".