Political tension in Iran following a tumultuous election ratcheted up a notch when a top aide of Iran's supreme leader called the country's main opposition figure a US agent and accused him of committing crimes against the nation in an editorial published Saturday. The editorial marked the first time that Mir Hossein Mousavi, who was the main challenger to incumbent Mahmoud Ahmadinejad in Iran's presidential elections on June 12, has been publicly called a US agent. Weeks of demonstrations erupted in Iran after Mousavi lost to Ahmadinejad, claiming the election was rigged; authorities maintain that the protests were instigated by foreign elements. "It has to be asked whether the actions of [Mousavi and his supporters] are in response to instructions by American authorities," said Hossein Shariatmadari in an editorial appearing in the conservative daily Kayhan. Shariatmadari, who holds no official position but is a close adviser to Iran's supreme leader Ayatollah Ali Khamenei, added that Mousavi was trying to "escape punishment for murdering innocent people, holding riots, cooperating with foreigners and acting as America's fifth column inside the country." He called for Mousavi and former reformist president Mohammad Khatami to be tried in court for "horrible crimes and treason." The editorial added that there were "undeniable documents" proving Mousavi's foreign links. When Iran's incumbent president was re-elected by a landslide, Mousavi and other opposition candidates cried foul sparking weeks of giant protests across the country that were eventually crushed. Police said 20 "rioters" were killed during the violence as well as seven or eight members of the paramilitary Basij militia tasked with putting down the protests. But the crackdown included severe limitations on press freedom, significantly against international news agencies and foreign reporters in the country. The number of dissidents killed or jailed cited by Iranian officials can therefore not be corroborated independently. There have been no street protests since Sunday, but Mousavi has maintained his opposition to the results, issuing a defiant statement on Wednesday that he considered the government "illegitimate" in a posting on his Website, and demanded political prisoners, which he called "children of the revolution," be released. He has been maintaining a low profile, however, and made no public appearances for days amid calls by many hard-liners for him to be prosecuted.