Police appealed to anti-capitalist protesters in California to abandon their camp after a fatal shooting, at least the fourth death this week in anti-Wall Street camps nationwide. The mayor of Oakland -- where violence has flared in recent weeks, at one point shutting one of America's biggest ports -- urged campers "to leave voluntarily" while police said they should disperse immediately. Deaths have also been reported in or near protest sites in Vermont, New Orleans and Salt Lake City, while police in Oregon have warned they will break up a camp in Portland this weekend. In Oakland a man was shot Thursday at the edge of the camp, apparently after a dispute, although the Los Angeles Times reported that Oakland Police Department indicated the victim may not have been part of the protests. The protesters are part of the "Occupy" movement that began near Wall Street in New York in September, then spread to cities nationwide, to demonstrate against perceived unfairness in the US economy and the power of big banks. Clashes first erupted in Oakland in October, leaving an Iraq veteran hospitalized, while protesters forced the busy international docks to close for 24 hours on November 2. Thursday's shooting occurred just as Occupy Oakland was celebrating the camp's one-month "birthday" -- turning the event into a candlelight vigil, amid renewed calls from critics for protesters to leave the downtown plaza. "You have sent the world a strong message; now it is time to go home," said the Oakland Police Officers Association, while Mayor Jean Quan added: "The risks are too great... We're encouraging people to leave voluntarily." During the day Friday -- Veterans Day in the US -- some 200 protesters including several dozen veterans marched in central Oakland chanting "Stop beating veterans!" and "Occupy Oakland! Not Afghanistan!" A message from the injured Iraq veteran, Scott Olsen, was read out to the crowd. "I wasted several years fighting overseas for the 1 percent," Olsen wrote in a statement spoken by veteran Aaron Hinde. Elsewhere a man was found dead Thursday in his tent at a protest camp in Burlington, Vermont, from what appeared to be self-inflicted gunshot wounds, according to police citing preliminary reports. Local police chief Michael E. Schirling said after the death that the demonstrators' "tents will need to be removed to ensure the safety of those involved in the protest, the public, and our law enforcement officers." In Utah, Salt Lake City police ordered protesters to vacate their camps after a man died overnight, apparently from a combination of carbon monoxide poisoning and a drug overdose, according to the Salt Lake City Tribune. Drug paraphernalia and a propane heater were retrieved from the victim's tent, it reported. And in Louisiana, a dead man was found Tuesday in his tent at the Occupy New Orleans encampment across from City Hall, the protesters' website said. Local news reports quoted the coroner's office saying the 53-year-old man, showing no signs of trauma, appeared to have been dead for at least two days before he was discovered. In Oregon, Portland mayor Sam Adams warned anti-Wall Street protesters that police will take action if five-week old camping areas are not cleared by midnight Saturday (0800 GMT Sunday). "Portland police are carefully preparing for this closure, and share my goal for an orderly and peaceful closure to the camps," he said.