Iran's rulers stiffened their stance against protesters Tuesday, firmly rejecting demands to annul the election over fraud allegations, setting up a special court for detained demonstrators, and keeping troops in riot gear on the streets to break up any gatherings. Opposition leader Mir Hossein Mousavi has not been seen in recent days and there were no reports of violence on Tuesday, perhaps a testament to the effectiveness of the crackdown. However, protesters came up with new techniques, such as turning on the lights in their cars at certain hours of the day and honking their horns or holding up posters. "People are calmly protesting, more symbolically than with their voices," a Teheran resident said in a telephone interview, speaking on condition of anonymity for fear of government retribution. In recent days, members of the elite Revolutionary Guard, the Basij militia and other security forces in riot gear have been heavily deployed across the capital, preventing any gatherings and ordering people to keep moving. A protest of some 200 people Monday was quickly broken up with tear gas and shots in the air, while helicopters hovered overhead. Mousavi claims he was the true winner of the June 12 election, but the electoral commission declared President Mahmoud Ahmadinejad won by a landslide (story continues under clips below). Watch Iranian policemen beat up a protester: More from youtube: . Another opposition figure, reformist presidential candidate Mahdi Karroubi, called for a day of mourning for the at least 17 people killed in protests since the election. The US and many European countries have refrained from challenging the election outcome directly, but have issued increasingly stern warnings against continuing violence meted out to demonstrators. UN Secretary General Ban Ki-moon has demanded an immediate end to "arrests, threats and use of force." However, the Iranian regime appeared determined to crush the post-election protesters, rather than compromise. Mousavi has charged massive vote fraud and insisted he is the true winner. However, Iran's top electoral body, Guardian Council, found "no major fraud or breach in the election," a spokesman, Abbas Ali Kadkhodaei, was quoted by Press TV as saying Tuesday. "Therefore, there is no possibility of an annulment taking place." The 12-member council has the authority to annul or validate the election. On Monday, it acknowledged in a rare step that it found voting irregularities in 50 of 170 districts, including vote counts that exceeded the number of eligible voters. Still, it said the discrepancies, involving some 3 million votes, were not widespread enough to affect the outcome. Iran has 46.2 million eligible voters, one-third of them under 30. The final tally was 62.6 percent of the vote for Ahmadinejad and 33.75 percent for Mousavi, a landslide victory in a race that was perceived to be much closer. The huge margin went against the expectation that the record 85 percent turnout would boost Mousavi.