Occupy protestors clashed with police in the city of Oakland, California, during their May Day strike on Tuesday.

Occupy protestors clashed with police in the city of Oakland, California, during their May Day strike on Tuesday.

Several hundred protestors blocked traffic near Oakland City Hall before police fired tear gas and flash-bang grenades, according to a report by local newspaper San Francisco Chronicle.

Police detained at least three people and used a Taser on at least one person after a crowd surrounded officers trying to make an arrest, said the report. Protestors threw plastic bottles at police officers in riot gear, breaking windows on a police van and a TV news van.

Scott Olsen, an Iraq war veteran who gained international attention when he suffered a brain injury from a beanbag shot by Oakland police in a protest last October, told San Francisco Chronicle that he was glad to be back protesting in Oakland but was worried about an aggressive police response.

The Oakland protest is part of the worldwide May Day demonstrations. In the U.S., several local branches of the Occupy Wall Street movement joined the protests.

Oakland is a major U.S. West Coast port city on San Francisco Bay. Last October, the use of tear gas and other projectiles on largely peaceful Occupy protestors made international news after Iraq war veteran Scott Olsen was injured.

Since then, Oakland has become one of the centers in Occupy movement in the U.S. Protestors successfully shut down operations at the Port of Oakland twice last year. In a protest this January, police arrested more than 400 Occupiers after the historic Oakland City Hall was vandalized.