BEIRUT — The Iranian authorities acknowledged Saturday for the first time that at least three protesters had been beaten to death in prison after the disputed presidential election in June, as a military court announced that 12 prison officials had been charged with murder and other crimes. The court’s statement followed months of denials by the police and prosecutors, who grudgingly conceded that some torture had taken place but attributed the deaths to meningitis or other illnesses. The statement was posted on the Web site of ISNA, a semiofficial news agency. The statement represented a vindication for the Iranian opposition, whose leaders have long accused the government of covering up savage abuses during the postelection crackdown. Opposition leaders say at least 73 people are known to have been killed in the unrest. The government has given varying totals, from 17 to 30, including members of its own security forces. Some in the opposition and abroad were skeptical that the charges would lead to justice. “There is a history of these kinds of trials that are announced as a result of a P.R. fiasco, but then go nowhere,” said Abbas Milani, the director of Iranian Studies at Stanford University and a strong critic of Iran’s leadership. The military court did not name the defendants. The deaths provoked outrage among conservatives as well as reformists, especially after the son of a prominent conservative political figure, Mohsen Ruholamini, died after being tortured in detention. The controversy led to a parliamentary inquiry and pushed the supreme leader, Ayatollah Ali Khamenei, to personally order the closing of the Kahrizak prison in Tehran, where Mr. Ruholamini was tortured. Opposition leaders also claimed that detainees were raped, citing detailed testimony from victims. The accusation was especially shocking in Iran’s Islamic culture and prompted angry rebuttals from conservatives. The 12 people charged all worked at Kahrizak, according to the military court’s statement. Three are accused of murder, with a possible death penalty. They were charged in the killings of Mr. Ruholamini and two other jailed protesters: Amir Javadifar and Mohammad Kamrani. The court said, “The coroner’s office rejected meningitis as the cause of death, confirming repeated beatings to the bodies, and concluded that those injuries were the cause of death.” The charges against the other nine defendants include abuse, negligence and depriving prisoners of their legal rights, the court said. It made it clear that the abuses went far beyond the three killings, saying that the Kahrizak center “lacked necessary standards for housing detainees, and that beatings by the guards worsened this bad situation.” The military court did not mention Ramin Pourandarjani, a young doctor who worked at Kahrizak and refused to sign death certificates he said were used to cover up murder there. Dr. Pourandarjani later testified to a parliamentary committee that jailers had tortured and raped prisoners, his family has said. He was found dead on Nov. 10, and government officials have given varying explanations, including suicide and poisoning. The military court inherited responsibility for investigating the abuses in September, after a parliamentary committee suddenly announced that it would instead forward the matter to the court. Although the court is part of Iran’s armed forces, it is not known to have any link to the Revolutionary Guards, which orchestrated much of the crackdown after the election. Although the Iranian authorities have never directly acknowledged that prisoners died from torture, the semiofficial Mehr news agency, citing “informed sources,” reported in late August that Iran’s chief medical examiner had determined that Mr. Ruholamini had died from beatings.