Around the world there were demonstrations by a loose collection of anarchists and leftists protesting third-world debt or the power of multi-national business, and police massed to protect public order and property.
"We're protesting for the way capitalism is threatening us today," said one protester in London.
The May 1 holiday celebrating workers brought out activists from a wide range of causes, but the growing anti-globalization movement often had a strong presence. The movement opposes liberalization of world trade that it says fuels poverty and damage to the environment while increasing corporations' power.
A pro-communist demonstrator in Moscow. (AP)
In London, thousands of demonstrators poured into the main shopping street to demand the government as one banner put it "overthrow capitalism and replace it with something nice."
They confronted police in riot gear and on horseback. Determined to avoid the destruction of last year's May Day march in London, police corralled the protesters in Oxford Circus.
As riot police with sticks and shields penned some 3,000 protesters into the intersection for about five hours, the widely predicted violence sputtered and flared. At about 8 p.m., police began to allow some demonstrators to leave. Police said they arrested 42 people.
In Berlin, police used water cannons to break up riots by some 500 protesters who overnight erected barricades, set fires and threw rocks and bottles at police.
During an afternoon march by some 1,500 anti-capitalist activists in another Berlin neighborhood, a few protesters threw cobblestones at police and smashed a telephone booth and bus stop. Police charged the rock-throwers, who retreated.
In Sydney, Australia, hundreds of anti-globalization protesters fought with police, leaving two officers hospitalized and 28 others injured. Brisbane police arrested about 35 activists and several people were injured as protesters tried to storm the stock exchange. Sydney police detained about 30 protesters and charged four.
Croatian workers, struggling to make ends meet in an economy mired in recession, celebrated in Zagreb with free bean stew in a downtown park. The president and the prime minister mingled with leaders of maor trade unions, promising better conditions.
"This May 1 is particularly important because of the string of layoffs organized by companies whose profits are rising," said Marcel Karbasse, a member of the CGT trade union.
In towns across Russia, an estimated 730,000 people joined marches and rallies though the 28,000 who turned out for two rallies in Moscow was a fraction of the number that used to jam Red Square in Soviet times.
Many of Tuesday's marchers carried red flags, portraits of Josef Stalin and other Soviet-era momentos to underline what they see as Russia's decline since the Soviet Union's fall in 1991.
In Istanbul, Turkey, 20,000 people marched, many urging the government to compromise with leftist inmates who are staging a month-long hunger strike over prison conditions. Twenty strikers have died so far.
In China, May Day marks the start of one of the year's biggest travel seasons. The government requires employers to give employees the rest of the week off, in part to try to stimulate the economy by encouraging travel.
In Seoul, 10,000 workers and students beating gongs and drums marched behind a large banner denouncing the president's economic reforms, reading: "Down with Kim Dae-jung, who ruined workers' lives."
In Bangladesh, thousands of workers with red ribbons tied around their heads marched through Dhaka, demanding minimum wages and better working conditions. The also called for free flow of workers across international borders.
About 20,000 Taiwanese workers, waving placards and purple banners reading "Give Me Work," marched through Taipei's government district demanding action to curb the island's jobless rate, which is at a 16-year high of nearly 4 percent.
In Cuba, Fidel Castro's government called for hundreds of thousands of workers to take part in a march past the U.S. government's mission in Havana. In a speech, Castro warned of an approaching cataclysm of American hegemony.
"How marvelous! Surely two or three Disneylands will be built in Central and South America!" Castro said.
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