[1/3] Iran's Supreme Leader Ayatollah Ali Khamenei speaks during a meeting with a group of students in Tehran, Iran November 2, 2022.
Badri Hosseini Khamenei, who lives in Iran and is the sister of Ayatollah Khamenei, criticised the clerical establishment starting from the time of the Islamic Republic's late founder Ayatollah Ruhollah Khomeini to her brother's rule, the letter, dated "December 2022", said.
"Ali Khamenei's Revolutionary Guards and mercenaries should lay down their weapons as soon as possible and join the people before it is too late," the letter said.
The Revolutionary Guards are Iran's elite force which has helped the country's establish proxies across the Middle East, and runs a vast business empire.
President Ebrahim Raisi meanwhile gave a speech at the University of Tehran to mark Student Day.