Over 1,000 Occupy Wall Street protesters returned to a public square late Wednesday in Oakland, California, one day after clashes with police left one demonstrator critically injured.

Activists say 24-year-old Iraq War veteran Scott Olsen suffered a fractured skull late Tuesday when riot police clashed with protesters attempting to hold a demonstration in the square from which they had earlier been evicted due to illegal camping activities.

Police used tear gas and bean bag bullets to disperse the protesters, some of whom were throwing rocks, paint and other debris at police.

Oakland Police Chief Howard Jordan on Wednesday announced an investigation into reports that his department used excessive force to disperse the protesters.

City officials say they will allow protesters to assemble from 6 a.m. to 10 p.m., but that no camping will be allowed overnight on public property.

Police arrested approximately at least 85 protesters during Tuesday night's clashes.

Meanwhile, activists say they are working with businesses, schools and unions to organize a citywide strike in Oakland next week.

The Occupy Wall Street protests, which began in New York last month, are part of a loosely organized movement protesting corporate greed, economic inequality and high unemployment.

Similar protest groups have sprung up in dozens of cities across America, as well as countries around the world.