In one of the biggest protests, enraged Iraqis in the southern town of Diwaniya on Friday swarmed over the local office of his political party, ripping down signs and throwing rocks.
A military offensive by US and Iraqi forces on the al-Mahdi Army of the Iraqi Shia leader Muqtada al-Sadr has inflamed passions among Iraqis and Muslims.
Willing to die
Thousands of supporters of al-Sadr, who was reported wounded on Friday in the besieged city of Najaf, marched through Baghdad, saying they were willing to die as his martyrs.
The crowd set out from the Shia leader's stronghold in the northeast of Baghdad, Sadr City, for the heavily fortified Green Zone, which houses some government offices.
The men chanted slogans such as "We want to be martyrs for you, Muqtada al-Sadr" and "He's the bridge to paradise" while making their way through the centre of the city.
Al-Sadr has a strong following in
the Baghdad suburb of Sadr City
"We want to hold a peaceful demonstration outside the convention centre" inside the Green Zone, said one of the protesters, who refused to give his name.
The men held aloft a sea of flags and carried banners reading "Shoot Down American Planes" and "Leave Muqtada al-Sadr".
Sunni Muslim support
The Najaf offensive has also infuriated residents of the Sunni-dominated town of Falluja, which has been a significant anti-US occupation spot.
About 3000 people marched in the centre of Falluja carrying pictures of al-Sadr and placards denouncing the US bombing of Najaf, where the cleric and his followers are surrounded.
"Long live Sadr. Falluja stands by Najaf against America," the marchers shouted.
South of Baghdad, in the small town of Kut al-Hayy, more than 1000 people - both Sunni and Shia Muslims - marched through the streets after Friday prayers to demand an end to bloodletting.
Sadr's local representative, Ashraf al-Husayni, called for an immediate end of the occupation and for the assault in Najaf to stop, as protesters held up a banner calling for the dismissal of the defence, interior and prime ministers.
Thousands of Iranians marched through the streets of Tehran on Friday in protest against US military actions in Iraq after a senior hardline cleric praised the resistance of Shia Muslims in Najaf.
Chanting "Death to America" and burning US flags, the protesters flooded streets in central Teheran carrying banners proclaiming: "Death to the occupiers" and "American democracy = massacre of innocent people".
Similar state-sponsored rallies were planned across the country.
"They (Americans) want to fully eliminate Islamic groups from the Iraqi scene and give power to a secular group who are US agents," Ayatollah Ahmad Jannati told worshippers at Friday prayers in Teheran before the protest march started.
"I must appreciate those who are resisting around the holy shrine (of Imam Ali in Najaf) against the bloodthirsty wolves," he said.
Al-Sadr's aide said he was injured
in US bombardment on Thursday
Jannati, who heads a powerful hardline constitutional watchdog, criticised Iraq's interim government for "giving the green light" to the US military to carry out raids against Shia fighters in Najaf.
But he made no direct reference to al-Sadr, whose supporters have been fighting US and Iraqi forces in Najaf for more than a week now.
A statement read by the protesters expressed "hatred for the occupiers' presence in Iraq and our support for the innocent Iraqi nation".
"Iran condemns the international community's silence on the crimes being committed by occupying forces in Iraq," it said.
One protester, Muhammad, 53, said it was the duty of Muslims to confront the US military in Iraq.
"America attacked Iraq and looted the country and now the Iraqis want to defend their rights," he said. "The Americans call them terrorists, but the Iraqi people are not terrorists, they (the Americans) are the real terrorists."
Scores of riot police surrounded the nearby British embassy where many of the marchers were expected to congregate later.
In the absence of a US embassy in Iran since Washington broke diplomatic ties in 1980, the British mission has borne the brunt of protests against US-led occupation of Iraq.
Jannati mocked accusations by some US and Iraqi officials that Teheran had been arming Shia rebels in Iraq.
"This is just another pretext against Iran. Could it be any more amusing than this?" he said.
Relations between the two neighbours, who fought a bitter 1980-1988 war, have been strained by the charges of Iranian meddling and by the arrest of several Iranian journalists and business people and the kidnapping of an Iranian diplomat in Iraq in recent weeks.