Protests at financial mismanagement and government cutbacks have been held in cities around the world.
At least 20 people were injured in clashes at the biggest rally, in Rome, as riot police fought masked militants who had attacked property.
Police used tear gas, water cannon and baton-charges, making several arrests.
Inspired by the Occupy Wall St movement and Spain’s “Indignants”, demonstrators turned out from Asia to Europe, but numbers were generally small.
Organisers expect rallies in 82 countries, with the protests due to come full circle when they reach New York.
Organisers said on their website that the aim was to “initiate the global change we want”.
“United in one voice, we will let politicians, and the financial elites they serve, know it is up to us, the people, to decide our future,” it said.
