Defeated Iranian presidential candidate Mehdi Karoubi said Iranian intelligence agents were handling detainees with harsher methods than Israel was deploying against the Palestinians, his website reported.
"The behavior of Iran's security agents is worse than those of the Zionist (Israel) in the occupied Palestine ... Can you put detainees under mental pressure in mosques, schools and in the basements of government offices?" Karoubi said in a letter addressed to Intelligence Minister Gholamhossein Mohseni-Ejei.
"What is happening to the people of Iran, especially the women, is deplorable," "Everyone has seen how the women have beaten with batons and thrown to the ground - this is worse than what the Zionist criminals are doing to the oppressed Palestinian people."
Meanwhile, Iran's opposition leaders appealed to the top clerics in the holy city of Qom on Saturday to pressure the ruling Islamic regime to release protesters and activists who they say have been tortured following last month's disputed presidential election.
The opposition hopes that enlisting the support of the clerics will provide an effective counterweight to Supreme Leader Ayatollah Khamenei, who has dismissed the opposition's claims of fraud in the June 12 election.
Khamenei has the final say over all state matters, but the nine clerics in Qom who hold the rank of "marja' taqlid," or "source of emulation," have great spiritual influence over many Iranians.
"We call on you, the marja' taqlid ... to remind the relevant authorities of the damaging consequences of employing unlawful methods and warn them about the spread of tyranny in the Islamic republic system," said the letter to the clerics, a copy of which was made available to The Associated Press.
Reuters and AP contributed to the story