Activists scuffled with police in London and decried the wealthy in Hong Kong on Saturday as an unprecedented outcry against corporate greed and government cutbacks spread worldwide.
Inspired by America's "Occupy Wall Street" and Spain's "Indignants", people took to the streets in a rolling action targeting 951 cities in 82 countries from Asia to Europe, Africa and the Americas.
It was the biggest show of power yet by a movement born on May 15 when a rally in Madrid's central Puerta del Sol square sparked a protest that spread internationally.
Anger over unemployment and opposition to the financial elite hung over the protests, which coincided with a Paris meeting of G20 financial powers pre-occupied by the eurozone debt crisis.
But the demands and the sense of urgency among the activists varied depending on the city.
Scuffles broke out in London where about 300 people rallied in the financial district by Saint Paul's Cathedral, raising banners saying: "Strike back!"; "No cuts!" and "Goldman Sachs is the work of the devil!"
Three lines of police, and one line at the rear on horseback, blocked them from heading to the London Stock Exchange and pushed back against lead marchers, some wearing masks.
"I am here today mainly as a sense of solidarity with the movememts that are going on around the world," said Ben Walker, a 33-year-old teacher from the eastern English city of Norwich.
"We're hoping for a kind of justice in the global financial system," the teacher said. He carried a sleeping bag and said he would spend the next night or two in the area.
In Madrid, 100 people in one of a series of five marches set off for an evening rally in the emblematic Cibeles square from where they will proceed to Puerta del Sol for all-night rallies.
"The fight goes on!" they chanted at the start of a six-hour march from the southern suburb of Leganes to the centre of Madrid.
Thousands more marched in Rome where 1,500 police patrolled, famous monuments including the Colosseum and the Roman Forum were closed down and four metro stations were shut.
"Today is only the beginning. We hope to move forward with a global movement," said one protester, Andrea Muraro, a 24-year-old engineering student from northern Padua.
A small group of about 50 protesters gathered outside of Africa's biggest bourse, the Johannesburg Stock Exchange, to voice concern over the country's widening gap between rich and poor.
"We need to stop the greedy wealthy elite from stealing from the poor working class," said "Occupy South Africa" organiser Marius Bosch.
As the day began, around 500 people gathered in the heart of Hong Kong's financial district to vent their anger at the inequities and excesses of free-market capitalism, while 100 demonstrators in Tokyo also voiced fury at the Fukushima nuclear accident.
Around 600 demonstrators in Sydney set up camp outside Australia's central bank, where the plight of refugees and Aboriginal Australians was added to the financial concerns.
Organisers of the worldwide protest, relying heavily on Facebook and Twitter, say demonstrations will be held in 951 cities across 82 countries in Europe, North America, Latin America, Asia and Africa.
The "indignant" protests first took hold in Spain, which has a jobless rate of 20.89 percent rising to 46.1 percent for 16- to 24-year-olds, where for a month activists lived in a ramshackle camp in Puerta del Sol.
They then spread elsewhere in Europe, finding strong backing in crisis-hit countries like Greece, and then worldwide -- last month reaching the centre of global capitalism in Wall Street.
In New York, where since September 17 several hundred people have occupied a small park in the financial district, organisers have called a rally in Times Square for 5:00 pm (2100 GMT).
The protesters declared victory Friday morning when New York authorities at the last minute postponed the evacuation of their camp.
But an impromptu celebration march to nearby Wall Street ended in scuffles and 14 arrests when protesters ignored police instructions to remain on the sidewalks so as not to impede traffic.
US police arrested about three dozen other protesters in Denver, Seattle and San Diego.
Over 100 authors, including Salman Rushdie and Pulitzer Prize-winning novelist Michael Cunningham, have signed an online petition declaring their support for the protests.