Supporters and opponents of Iranian President Mahmoud Ahmadinejad clashed for a second night in Tehran on Saturday.
The incident followed a televised debate between the president and challenger Mehdi Karoubi. A presidential election is to be held on 12 June.
Thousands of supporters of Mr Ahmadinejad and another of his moderate challengers in the presidential election earlier clashed in the capital on Friday evening.
Mr Ahmadinejad is being challenged by Mr Karoubi, former Prime Minister Mirhossein Mousavi, and the former head of the Revolutionary Guards, Mohsen Rezaie.
Mr Mousavi, a moderate, is seen as the president's main opponent.
Mr Ahmadinejad's critics say his anti-Western speeches and questioning of the Holocaust have isolated Iran, which is at odds with the West over its disputed nuclear programme.
Iran says it is for electricity generation, but a number of Western countries believe the aim is to build nuclear weapons.
Mr Ahmadinejad accuses his rivals of trying to weaken Iran by advocating detente with the West.