Iran's deputy police chief said on Wednesday that the nephew of opposition leader Mir Hossein Mousavi was assassinated by unidentified assailants and not killed by security forces. Ali Mousavi was one of at least eight people killed during clashes Sunday when tens of thousands of opposition supporters protested against the government. The opposition says Ali Mousavi was shot and killed by security forces. But Iran's deputy police chief, Ahmad Reza Radan, is quoted by the official IRNA news agency as saying that the way he was killed suggests he was assassinated while walking. The New York Times has quoted a family friend as saying Ali Mousavi was run over by a vehicle outside his home in an assassination. Iranian hard-liners meanhwhile called for a series of state-sponsored demonstrations on Wednesday in what they hoped would be a massive show of strength against the reformist movement, while the country's police chief threatened to show "no mercy" in crushing any new opposition rallies. Wednesday's hardline protests, planned in Teheran and several other cities, were the latest official response to what has become the boldest challenge to the ruling system since the Islamic Revolution 30 years ago. The government has been systematically arresting top opposition activists, including the sister of Nobel peace laureate Shirin Ebadi, limited the movement of a top opposition leader and heavily restricted media coverage in the wake of opposition rallies that left eight people dead early this week. Iran's police chief, Gen. Ismail Ahmadi Moghaddam said authorities had exhausted their patience with the opposition and promised tough new action. "In dealing with previous protests, police showed leniency but given that these currents are seeking to topple [the ruling system], there will be no mercy. We will take severe action," the official IRNA news agency quoted him as saying. "The era of tolerance is over. Anyone attending such rallies will be crushed." Tens of thousands of people were expected at Wednesday's demonstrations, which were set to begin at mid-afternoon. For several days, hard-liners have been imploring supporters to attend, and officially organized buses were transporting groups of schoolchildren, civil servants and supporters from outlying rural areas to the protests. Sunday's deadly protests coincided with Ashoura, the most solemn day of the year for Shi'ite Muslims. The observance commemorates the 7th-century death in battle of one of Shi'ite Islam's most beloved saints, and it conveys a message of sacrifice in the face of repression. Hard-liners are especially furious that some of the protesters insulted the supreme leader, Ayatollah Ali Khamenei, casting aside a taboo on personal criticism of the leader. The government has said the protesters are a tiny minority, and accused the US and Britain of organizing the opposition. The hard-line criticism has become increasingly vocal, with some activists threatening to take the law into their own hands. Hardline cleric Abbas Vaez Tabasi, a Khamenei representative, accused opposition leaders on Tuesday of being "enemies of God" who should be executed. "In our judiciary system, the verdict for mohareb is clear," he said. Under Iran's Islamic sharia law, the sentence for a "mohareb," or enemy of God, is execution. Iranian President Mahmoud Ahmadinejad shrugged off new opposition protests Sunday as "a play ordered by Zionists and Americans" and criticized Barack Obama and Britain for allegedly supporting the protesters. "The Iranian nation has witnessed this sort of play many times," Ahmadinejad said, according to the state IRNA news agency. Government supporters held rallies in at least three cities on Tuesday, many protesting against the opposition and its leaders. Opposition Web sites reported about 10 new arrests Tuesday, and those taken into custody included the sister of Ebadi, who won the 2003 Nobel Peace Prize for her human rights efforts in Iran. Ebadi, who has stayed outside of Iran since a day before the June elections, told The Associated Press in a phone interview from London that Iranian authorities were trying to punish her by arresting her sister. The new arrests, along with the tough criticism of the US and Britain, added to rising tensions with the West, which is threatening to impose tough new sanctions over Iran's suspect nuclear program and has criticized the violent crackdown on anti-government protesters. The opposition Rah-e-Sabz, or Green Road, Web site reported additional arrests, among them opposition leader Mir Hossein Mousavi's brother-in-law, Shapour Kazemi, and Mashallah Shamsolvaezin, a journalist who frequently criticizes the government. Iranian security forces also limited the movements of leading opposition figure Mahdi Karroubi by refusing to protect him when he leaves his home. Police have for years provided leading opposition figures with security. Without the guards, he cannot go outside safely and is under a "quasi-house arrest," said his son, Taghi Karroubi. If Karroubi leaves unprotected, he risks attack by hardline government supporters. His car was attacked on Saturday when he went out, and assailants shattered his front windshield. Karroubi and Mousavi were the two defeated reformist candidates in the disputed June 12 presidential election, which set off the worst unrest in Iran since the 1979 Islamic Revolution.