3 of 18

Occupy Wall Street participants stage a march in New York. The Occupy movement that shook the United States last year, spawning similar protests worldwide, announced widespread May Day demonstrations and strikes against social inequality. The protests, billed as stretching from New York to California, and from Spain to Australia, raised the possibility of disruption in dozens of urban centers.

5 of 18

A protester gestures during a rally for International Worker's Day outside the Alameda County Court House in Oakland, California.

7 of 18

A person dressed in a skirt made of fake money joins participants of Occupy Wall Street during a May Day demonstration march at Bryant Park in New York City.

9 of 18

A protester is taken into custody at a rally in Oakland, Calif.

11 of 18

Demonstrators gather around a fire in Lindenstrasse during a May Day anti-capitalism protest in Berlin, Germany. This year marks 25 years since a 1987 Berlin May Day demonstration turned violent and has been followed by clashes between participants and police on May Day in Berlin almost every year since.

13 of 18

Protesters hold a rally inside the Tom Bradley terminal of Los Angeles International Aiport during a May Day march. Workers at Los Angeles International Airport went on a one-day general strike to protest what labor activists are calling unfair practices by airlines using hired contractors instead of unionized employees.

15 of 18

Ricky Evangelio protests while working his ice cream cart during a May Day march in Chicago, Ill. Approximately 1000 people in Chicago joined in the march which worked its way for about two miles from the city's West side into the Loop.

17 of 18

An Occupy protester holds a rose in front of Oakland police officers.