The Iranian government and opposition leader Mir Hossein Mousavi stepped up their war of words Sunday after at least 10 people were killed in clashes on Saturday, while an uneasy calm prevailed on the streets of Tehran on Sunday for the first time since Iran's worst political crisis in 30 years began a week ago. Government media lashed out Sunday at Mousavi, suggesting that some of his actions were illegal and blaming 'terrorists' for Saturday's violence, in which at least 100 people were injured. The semiofficial Fars News Agency, which has strong ties to the government of President Mahmoud Ahmadinejad, quoted a law professor at Tehran University as saying that Mousavi's actions were criminal. 'Through uncivil and illegal means, he created an environment for unrest and hooliganism,' Firouz Aslani told Fars News. 'Contrary to his claims of lawfulness, he acted against the security of the nation and the interests of the system.' Some analysts in Tehran said those comments and others carried in the state-run news media questioning the legality of Mousavi's actions could be the government's way of preparing the ground for his arrest. Mousavi, 67, a former prime minister who has alleged that the June 12 election officially won by Ahmadinejad was riddled with fraud, made no public appearances Sunday. But he responded to statements against him by condemning the government's use of force against protesters and urging his supporters to stay calm. 'The heart-rending news of the martyrdom of yet another group of protesters to the recent fraud in the elections put our nation in shock and sorrow,' Mousavi, who has become the face of a broad and deep protest movement that has drawn hundreds of thousands of people into the streets, argued in a posting on his banned newspaper's Web site. 'Shooting at the people, militarizing the city, scaring the people, provoking them, and displaying power are all the result of the unlawfulness we're witnessing today,' he wrote, arguing that Iranians have the right to peaceful protest. In Washington, President Obama made no public statements on the Iran unrest Sunday; on Saturday, he had made his most forceful comments to date on the issue, calling on the government in Tehran to stop its 'violence and unjust' crackdown. On Sunday television talk shows, several Republican lawmakers criticized Obama's response to the situation. 'I appreciate what the president said yesterday, but he's been timid and passive more than I would like, and I hope he will continue to speak truth to power,' Sen. Lindsey Graham, R-S.C., said on ABC's 'This Week' program. 'Anytime America stands up for freedom, we're better off. When we try to prop up dictators or remain silent, it comes back to bite us.' 'If America stands for democracy and all of these demonstrations are going on in Tehran and other cities over there, and people don't think that we really care, then obviously they're going to question: Do we really believe in our principles?' Sen. Charles Grassley, R-Iowa, said on CNN's 'State of the Union.' Administration officials have said Obama has been careful in his response to avoid giving the Iranian government an excuse to portray the protesters as U.S.-backed pawns. Although Tehran was quieter Sunday, eyewitnesses reported gunshots and sirens in the central neighborhood of Abbas Abad. A large column of black smoke could be seen rising up from the area. Eyewitnesses also reported unrest in central Haft-e Tir Square. Few senior aides to Mousavi could be reached for comment. Several have been arrested, are not answering their phones or are turning their backs on Mousavi after Friday's warning by Ayatollah Ali Khamenei, Iran's supreme leader, that protesters faced bloodshed if they continued their mass demonstrations. 'Nothing is certain now,' said Hassan Baghernejad, a senior Mousavi campaign official. 'Some people have accepted the definitive response by the supreme leader; others haven't. We must wait and see.' As Mousavi's supporters consider their options, the government media offensive is accelerating. The official Islamic Republic News Agency carried a lengthy article on Mousavi and quoted Alireza Zahedi, a member of the pro-government Basij militia, as saying that Mousavi instigated the unrest 'because he didn't have a following among the people.' Authorities appeared to be seeking to blame the violence on radicals. Iranian state television charged that 'the presence of terrorists ... was tangible' at Saturday's events. It asked viewers to send video recordings of protesters to help authorities make arrests. State television reported that 10 people died Saturday when clashes broke out between security forces and Mousavi supporters assembling for a rally that authorities had banned. First reports said that as many as 13 people had died, but the toll was later reduced to 10. Foreign journalists have been banned from covering the protests. Iranian police officials said 457 people were arrested -- some with the help of local residents -- during the protests Saturday, according to Mehr News, a semiofficial Iranian news agency. The agency also reported that 40 policemen were injured, 34 state buildings were damaged, and three buses and four private cars were set on fire during the violence. Saturday's death toll, which brought the number of fatalities in a week of protests to at least 17, added a potentially catalyzing element to the unrest. During the revolution that overthrew the shah of Iran in 1979, ushering in an Islamic republic, a cycle of protests, violent repression and more demonstrations to mourn the victims helped sustain and fortify the opposition. Mousavi referred to those protests in his statement Sunday. 'Should the revolutionary people, who with similar gatherings and protests freed us from the forgotten history of oppression of the shah, be beaten and frightened and be challenged to a power struggle?' Mousavi asked. He also complained that the names of those killed, wounded and arrested were not released. 'It only further stirs feelings,' he said. Another statement on one of Mousavi's campaign Web sites denied news reports that he had said he was ready for 'martyrdom' in the name of the protesters' cause. Scenes from Saturday's violent protests were shown frequently on Iranian state television and in a special broadcast the rioters were said to be members of the Paris-based Mujaheddin-e Khalq, an Islamist Marxist group that the United States has labeled a terrorist organization. The group, which sided with Iraqi dictator Saddam Hussein during the Iran-Iraq war of the 1980s and conducted a series of terrorist attacks, has little support among most Iranians. Audio clips were played of alleged recordings of telephone calls in which people said to be members of the organization urged others to pass on information about the protests to Western news organizations. But the group's involvement seems highly unlikely because its supporters are rare in Iran. Also Sunday, state-run news media reported the arrest of the eldest daughter and four other relatives of former president Ali Akbar Hashemi Rafsanjani, a Shiite Muslim cleric who heads two powerful groups in Iran's theocratic governing system. Rafsanjani has emerged as a strong critic of Ahmadinejad. The unrest has focused attention on the political maneuvering inside Iran's normally opaque power circle, especially between Rafsanjani and Khamenei, who announced Friday that he supported Ahmadinejad. In a rare show of criticism, the speaker of Iran's parliament, Ali Larijani, said the Guardian Council, the elite group charged with certifying elections, should not side with one candidate. Larijani is known for his loyalty to Khamenei. 'Although the Guardian Council is made up of religious individuals, I wish certain members would not side with a certain presidential candidate,' said Larijani, according to a Web site affiliated with him. 