Iran's supreme leader Ayatollah Ali Khamenei called on Saturday on the country's various groups to set aside their differences and work for the progress of the country. But reports of a death in prison of one of several people arrested following June's disputed presidential election stirred up the opposition anew. “The issues in the recent days should not be a reason for differences,” Khamenei said in an address telecast live on state television. “All of you should work in a brotherly way for the progress of the nation. Nobody should accuse the other without any reason. We should be fair in treating each other. We should put aside difference of opinions.” The re-election of President Mahmoud Ahmadinejad has rocked Iran with opposition groups refusing to acknowledge his victory. On Saturday, opposition leaders urged senior clerics in Qom to pressure the ruling regime to release protesters and activists who they say have been tortured following the disputed June 12 elections. A reformist website said the son of an adviser to defeated conservative candidate Mohsen Rezaie had been killed in a Tehran prison after being detained in post-election unrest. The authorities were not immediately available to confirm the death or the circumstances surrounding it. The opposition hopes that enlisting the support of the clerics in Qom will provide an effective counterweight to Khamenei, who has dismissed claims that Ahmadinejad won the June 12 election through massive vote fraud. The nine clerics in Qom who hold the rank of “marja' taqlid,” or “source of emulation,” have great spiritual influence over many Iranians. The clerics often congratulate election winners, but only one has done so this time. Three others have spoken out against the violent crackdown on hundreds of thousands of supporters of opposition leader Mir Hossein Mousavi. Mousavi, who claims he won the election, former President Mohammad Khatami and 67 other prominent reformists sent a letter to the clerics Saturday saying authorities have held protesters and activists without charges and have used torture to extract confessions. “We call on you, the “marja' taqlid” ... to remind the relevant authorities of the damaging consequences of employing law-evading methods and warn them about the spread of tyranny in the Islamic republic system,” said the letter. Saturday's turmoil coincided with Ahmadinejad caving in to hardliners and sacking his controversial first vice president Esfandiar Rahim Mashaie, a little over a week after he was appointed to the post. “I am sending you the letter of Rahim Mashaie announcing he is stepping down from the post of the vice president,” Ahmadinejad wrote to Khamenei in the letter, IRNA news agency said. Khamenei had himself ordered the sacking of Rahim Mashaie, who caused a stir last year when he said Iran was a “friend of the Israeli people.”