TEHRAN (AFP/Reuters) - Irans main opposition leader Mir Hossein Mousavi vowed more anti-government protests as the authorities announced several arrests on Monday over a reported insult to Islamic revolution founder Ayatollah Khomeini. Mousavis defiant call came a day after Irans supreme leader Ayatollah Ali Khamenei issued a stern warning to opposition leaders and accused some of them of battling against the Islamic regime. The opposition has denied involvement in the reported incident, suggesting the authorities were planning to use it as a pretext for a renewed post-election crackdown on dissent. Those people who were at the site have all been identified, Tehran prosecutor Abbas Jafari Dolatabadai said, quoted by ISNA news agency. He said arrests had been made, including one on the day of the student rallies, without giving names or numbers. They are all in detention and one of them has confessed, Jafari Dolatabadi said. The prosecutor also said there would be no mercy towards those who insulted the founder of the revolution, the official IRNA news agency reported. People have a right to question, they should not be confronted violently, Mousavi was quoted as saying by Rahesabz.net, one of three main websites that report on the opposition. From now on, all protests and demands should be pursued peacefully and lawfully. Nobody among us should make a pretext for those who are against people, he said. If peoples questions were answered and they were not confronted violently, we would not see some controversial moves today, Mousavi was quoted as saying. People want an end to the security-obsessed atmosphere as in such an atmosphere radicalism grows. Meanwhile, Iran on Monday denounced US President Barack Obama for making absurd comments and paying tribute to Iranian anti-government protesters when he was awarded the Nobel Peace Prize. Foreign Minister Manouchehr Mottaki told the official IRNA news agency that the US president has resumed making absurd comments because he is confused in his analysis of the situation. He warned that Obama and the American nation will face more dangerous and complex consequences if the wrong understanding continues, and as a result of mistakes made under (former US president George W.) Bush. Iran said on Monday it does not insist on exchanging its low-enriched uranium for fuel for a research nuclear reactor on its own territory after the United States bluntly dismissed the offer. The Islamic republic does not insist on accepting its own proposal of exchanging 400 kilos of uranium on Kish island in the Gulf, Foreign Minister Manouchehr Mottaki was quoted as saying by the Fars news agency. This proposal, which was previously discussed in bilateral talks, was offered by Iran as a goodwill gesture. On Saturday Mottaki had proposed that such an exchange take place on the southern Gulf island, a free trade zone, saying this could be an initial step in a process that would take several years. He said the process could begin right away if the United States, Britain, France, China, Russia and Germany agreed. Iran is to put on trial three US hikers arrested after they illegally entered Iran four months ago, Mottaki. Interrogation of the three Americans who have illegally entered Iran with suspicious aims is ongoing. They will be put on trial by the judiciary and rulings will be made, Mottaki told a press conference carried live on state television. Shane Bauer, 27, Sarah Shourd, 31, and Josh Fattal, 27, were arrested July 31 after straying into Iranian territory during a hiking trip in Iraqs Kurdistan region. Israeli Defence Minister Ehud Barak on Monday called for tough sanctions against Iran, which he said was seeking to gain time to build a nuclear weapon. We think it is still time for diplomacy, hopefully tough diplomacy with tough sanctions, preferably under Chapter 7, Barak said on a visit to the Austrian capital, referring to an article in the United Nations Charter regarding the action to be taken in cases of threats to peace and acts of aggression.