In an apparent sign of Iranian President Mahmoud Ahmadinejad and his ruling party flexing their muscles ahead of next week's UN General Assembly, the hard-line leader again denied the Holocaust, while two top reformists were attacked in Teheran.
Tens of thousands of Iranian government supporters and dozens of opposition activists poured out onto the streets of the capital for coinciding marches marking Quds Day - an annual event dedicated to condemning Israel and expressing support for the Palestinians. Quds is Arabic for Jerusalem.
Addressing government supporters, Ahmadinejad called the Holocaust "a false pretext to create Israel."
He said that "confronting the Zionist regime is a national and religious duty," and that Israel "has no future."
At the scene of the opposition march, a group of Iranian hard-liners attacked the car of former presidential candidate Mir Hussein Mousavi forcing him out of the area, according to AFP and Mousavi's Web site.
They also attacked reformist former president Mohammad Khatami while he was marching with the opposition supporters at the anti-government rally.
A reformist Web site cited witnesses as saying the attackers pushed Khatami to the ground. It said opposition activists rescued him and quickly repelled the assailants.
Khatami has sided with the opposition in the post-election crisis that has gripped Iran. Another reformist Webs site says his turban was disheveled and he was forced to leave the march.
The opposition insisted on holding its own protest, despite warnings by the clerical establishment against anti-government rallies.
There has not been a mass opposition demonstration since mid-July, when authorities cracked down heavily on the opposition.
On Thursday, Iran's elite Revolutionary Guard warned opposition protesters against holding anti-government demonstrations, saying that if they attempted "any sort of violation and disorder" they will encounter "strong confrontation."
Khamenei, who has final say on all state matters, last week also warned the opposition against using Quds Day for other purpose than demonstrating solidarity with the Palestinians.
The pro-reform camp claims Mousavi was the rightful winner of the June 12 presidential election and that the government faked the balloting in Ahmadinejad's favor. Since the vote, thousands of opposition supporters held street demonstrations against the alleged vote fraud but were met with a heavy government crackdown.
The opposition says at least 72 protesters were killed in the violence that followed the election, while government officials maintain that only 36 died in the unrest - the worst in Iran since the 1979 Islamic Revolution that brought the current regime to power. Thousands were arrested, and the regime's opponents have charged some detainees were tortured to death in prison.
Customarily on Quds Day, Teheran residents gather for pro-Palestinian rallies in various parts of the city, march through the streets and later converge for the prayers ceremony. The ceremony was established in 1979 by the leader of the Islamic Revolution and founder of present-day Iran, Ayatollah Ruhollah Khomeini.