From the streets of San Francisco to the cities of Bangladesh, millions unite to voice their protests

Demonstrations against the war in Iraq erupted on every continent yesterday. Millions of people opposed to the United States-led military invasion abandoned their work or studies and took to the streets.

Most protests were peaceful although a handful became violent, usually when police in riot gear sought to keep marchers away from American embassies and consulates. In some Muslim countries, the protests gave renewed vigour to Islamist political parties that are using the war as a recruiting tool.

In the West ­ including the US ­ participants expressed their concerns that the Bush administration was recklessly leading the world to a more unstable future.

In Brussels, around 3,000 people protested as European Union leaders were opening a summit to discuss the Iraq war. Four people were detained for throwing rocks at the US embassy and police used water cannons when a burning object was thrown at the American flag outside the embassy.

"Stop the Bush fire," they chanted in Berlin. "US warmongers go to hell!" read a banner in Calcutta. In Cairo, the largest city in the Arab world, anti-American sentiment accompanied expressions of anger at the country's leadership, which is pro-American and a big recipient of US aid. The discontent highlights the danger of political upheaval across the Middle East in the wake of the war.

"Down with Arab leaders!" the crowd chanted, as riot police used water cannon to prevent about 1,000 students armed with stones from approaching the US embassy. Cries of "Leave, leave Mubarak!", a reference to the Egyptian President, Hosni Mubarak, could also be heard.

Mr Mubarak and his security forces have given an increasing degree of leeway to anti-war protesters in recent weeks, perhaps to create an outlet for growing anti-government sentiment. But that did not stop police near the US embassy from swinging at protesters' heads with batons.

Other protests scattered across the Arab world included 1,000 women and children burning US and Israeli flags in the Gaza Strip and a clash between riot police and 1,000 demonstrators outside the British embassy in Beirut.

In the Philippines, riot police used truncheons to break up a small group of protesters who burnt an American flag and portraits of President George Bush and Gloria Arroyo, the President of the Philippines. She has stood staunchly by the United States in the war on terrorism.

In Indonesia, a Muslim party organised a rally in Jakarta while in Semarang, Java, police clashed with 50 students after they burnt an effigy of the US president.

In Pakistan, protesters denounced "American terrorism", and in Bangladesh left-wingers and Muslim politicians joined hands as they burnt US and British flags.

Italy's three biggest unions organised a two-hour general strike. "We want to bring cities to a standstill," said Luca Casarini, a union organiser. "We don't want people to get used to the idea of war, to think that it is normal."

Demonstrators peacefully occupied train tracks in Turin, blocked a motorway in Barcelona, marched through the Brandenburg Gate in Berlin, and flooded through Athens streets. Many of the hundreds of thousands of participants were schoolchildren.

Riot police in Geneva fired tear gas and rubber bullets on a crowd of 500 high school and university students marching towards the US mission to the United Nations. "Non à la Busherie!" they chanted, playing on the French word for butchery.

In the United States, much of the anti-war sentiment that gave rise to hundreds of protests in towns and cities across the country a month ago has subsided as people feel obliged to support the troops and pray for their safety. But the anti-war spirit was very much alive in San Francisco, where hundreds of protesters, many of them linked with metal pipes, blocked streets and motorway slip roads to disrupt morning commuters and initiate what they described as a "festival of resistance".

Participants received a hasty training session early yesterday on non-violent disobedience before taking up their posts. Hundreds of cars and dozens of buses were held up in traffic jams. Much of the financial district was surrounded. "We can't just go on with our lives when people are dying,'' said Carol Maddox, an occupational therapist.

At some intersections, protesters stood placidly as the police hauled them off. At others, the police simply kept watch as the participants chanted slogans. "Bush, you liar, we're going to set your ass on fire," one banner read.

In Washington, a much smaller group of about 150 protesters temporarily shut down the inbound travel lanes of a road running across the Potomac river. About 50 more cycled into central Washington with signs reading "bikes not bombs", and outside the White House a further 50 demonstrators shouted: "No blood for oil!"

While the police were generally patient with the protesters, the onset of the war has changed the mood at American military bases. In response to plans for a demonstration at Vandenberg Air Force base in central California this weekend, officials warned that anyone found trespassing would be subject to a new shoot-to-kill policy.