Occupy Wall Street protesters have staged rallies across the US as they called for a nationwide general strike to mark International Workers' Day.
Thousands gathered to protest peacefully in Union Square in New York City. That rally came hours after arrests and a confrontation with police on the city's Fifth Avenue. In Oakland, California protesters clashed with police as flash-bang grenades and tear gas were used.
Demonstrations and strikes were also held in Washington DC, the Los Angeles International Airport, Atlanta and in Chicago, where about 2,000 activists marched through the city to callfor immigration reform.
The Occupy movement won national attention in late 2011 with widespread protests against economic inequality. The May Day activities marked the most visible action from the group since authorities dismantled their main camps across the US last year.
An organiser in New York said the mood had changed. "There was a sense of novelty to Occupy in October," Mark Bray told the Associated Press. "Today is more celebratory, and nostalgic."