Iranian riot police on Tuesday arrested dozens of pro-reform protesters in central Teheran, Reuters cited a witness as saying, after hundreds of demonstrators gathered on the streets of the Iranian capital. "There are hundreds of riot police and plainclothes officers, beating people who gathered to support (opposition leader Mir Hossein) Mousavi," the witness reportedly said. "There are hundreds of protesters at Haft-e Tir square." The witness told the news agency that demonstrators were chanting slogans against Iranian President Mahmoud Ahmadinejad and the government, including: "Ahmadinejad - resign, resign" and "Death to dictators." "Riot police are taking dozens of protesters into their cars and they are taking them away," the witness was quoted as saying. Tweets posted on Twitter, which cannot be verified, suggest that around 10,000 people are involved in the demonstrations in four main areas of central Teheran: "Vali Asr; 7 Tir; Coledge Sq; Baharestan". According to Sky News, one tweet says: "A young lad with a phone nr Cinema was grabbed by security. Crowd freed him while fighting off teargas attacks. "As the crowd gathered near the cinema, guards showed force by beating an elderly person, crowd came to rescue." Tuesday's protests come days after clashes between police and protesters for the first time in weeks on Friday, after former President Akbar Hashemi Rafsanjani declared the Islamic Republic in crisis and said there were doubts about the election result.