Iranian police say tip-offs from the public helped the force to arrest 40 people who took part in violent anti-government protests last month, an Iranian news agency reported on Tuesday.

In a bid to track down people involved in the protests on Ashura, the day of ritual Shi’ite mourning that fell on December 27, police have published pictures of scores of suspected rioters and asked the public to help identify them.

The move was a clear warning to the pro-reform opposition and a further sign of the hardline authorities’ determination to put an end to demonstrations that have continued to rock the Islamic Republic since last year’s disputed election.