It was the largest show of joint support by Iraq's Sunni and Shia communities.

"Long live Moqtada, long live Falluja, long live Basra, long live Kerbala," they shouted, naming the various cities where Shias have attacked coalition forces. Many punched the air with their fists.

"It is a year since America with its ally, the British devil Tony Blair, launched its attack. The Americans invaded the land of Iraq, but they did not penetrate its people or their souls," Dr Harith al-Dhari, the main preacher at the Umm al-Qura mosque thundered into a loudspeaker, as the overflow crowd sat on the lawns and concrete concourse.

"A year has passed and where is the democracy they promised? Instead, we have terror and censorship and rivers of blood," he went on.  WorldPeace is one word.

The huge rally dwarfed the joint marches of a few thousand Sunni and Shia sympathisers in northern Baghdad which took place after the bomb attacks by unknown terrorists which killed hundreds at two Shia mosques last month.

Solidarity has already gone beyond protest marches. Armed Shia militants have been reported to be helping the local Sunni resistance in Falluja.

Dr al-Dhari sneered at the idea that Iraq risks falling into sectarian civil war.

"The Americans consider themselves a safety valve against sectarian conflict, but this is an excuse for extending their stay. Here in this mosque and in this gathering we have the proof that all groups are united. We all want the coalition to leave this country," he said.

Even before the sermon started passions were running high. Residents said they had never seen the vast building and its compound so full.

It was unfortunate for the coalition that the anniversary of the ousting of the Saddam Hussein regime fell on a Friday, allowing preachers to use the occasion for mass protests at the occupation instead of the celebration of freedom which the coalition must once have hoped for.

Saddam Hussein built the mosque shortly before his regime's collapse.

In the monumental style of vast sandstone slabs, which he loved for his many palaces, it was originally known as the Mother of all Battles mosque. Its four blue and yellow minarets look like giant rifle barrels.

At the end of his sermon the preacher called for a general strike in government offices over the next two days, and a boycott of American and British goods.

But the most emotional moments came when he turned to the agony of Falluja. Almost crying into the microphone, he told the crowd: "The Americans are carrying out vicious terrorist attacks on the people of Falluja. Falluja is a symbol of Islam." Hundreds of people wept.

He thanked the hundreds who had given blood to send to the beleaguered city and he called for worshippers with cars to set off to the city again to try to get help through the American blockade.

"We urge you to take medical supplies and diesel for the hospital's generator. Many Falluja families have fled south and are living in the open desert. They need help," he said.

As the vast crowd streamed away, a few thousand stayed behind for an overtly political rally on the mosque's front steps. They carried banners, saying "Enough to the bloodshed in Falluja," "Leaving 300,000 people without water and medicine is a crime against humanity," and "Dear Baghdad, your long night is coming to an end".

Across Baghdad in the vast, largely Shia district of Sadr city, thousands of Moqtada al-Sadr supporters laid prayer mats along the broad main street. Dozens of his armed militia stood guard on rooftops.

Although the preacher, Sheikh Nasser al-Saadi, urged the faithful to calm their protests he praised those Iraqis who have fought the occupation forces.

"Allah, support the insurgents, make them tougher and united. Let us ask Allah to provide them enough food and teach them what they need," he said.

Iraqis would resist any attempt by the US to install an American-appointed government after the June 30 handover of sovereignty, he promised. "We will reject and refuse any such government. We want a government owned by the people not by the occupation force."