Media playback is unsupported on your device Media caption Police dismantle Oakland Occupy tents in Oakland's Frank Ogawa Plaza

Police have shut down a camp set up by Occupy protesters in the California city of Oakland, dismantling tents and arresting 33 people.

Hundreds of protesters later marched back to Frank Ogawa Plaza and several said they would set up tents again.

A similar raid ended with police in riot gear arresting 50 people in Portland, Oregon on Sunday evening.

Police in a Vermont city have also evicted protesters after a man fatally shot himself last week inside a tent.

Business owners in New York meanwhile urged authorities to clear out the original Occupy Wall Street camp in that city.

'Crime scene'

Police declared the Oakland plaza a "crime scene" shortly after Monday morning's arrests and cleared media from the area.

Hours before the raid, a legal adviser to Oakland Mayor Jean Quan resigned via Twitter, saying he supported Occupy Oakland.

The protest has been marred in recent weeks by outbreaks of violence.

A 25-year-old man, Kayode Ola Foster, was shot dead near the plaza on Thursday evening.

His family confirmed to police he had been a resident of the Occupy Oakland camp.

There are thousands of people who are going to come back Ohad Meyer, Occupy Oakland

Oakland police said witnesses have told them that one of two suspects in the shooting also stayed at the plaza encampment.

Up to 1,000 protesters marched back to the Oakland plaza outside city hall on Monday evening.

"In case you haven't heard, we're already back in OG Plaza!" @occupyoakland said on Twitter.

Ohad Meyer, an Oakland resident, earlier told the Associated Press: "There are thousands of people who are going to come back."

In Oakland and elsewhere, city authorities said protesters could continue to gather at public plazas as long as they did not attempt to re-establish camps and stay overnight.

Oakland Mayor Jean Quan has come under criticism for her handling of a previous attempt to clear the protesters, in which an Iraqi war veteran was wounded.

Scott Olsen, 24, suffered a skull fracture on 25 October and his case became a rallying point for protesters across the country.

Mr Olsen confirmed on Google+ on Monday that he was home from hospital.

"After my freedom of speech was quite literally taken from me, my speech is coming back but I've got a lot of work to do with rehab," he said.

'Bags of excrement'

On Sunday, protesters peacefully vacated a park in Burlington, Vermont, days after a 35-year-old military veteran committed suicide in a tent there.

But the eviction in Portland was not so amicable.

Mayor Sam Adams ordered the camp to be shut down on the grounds that "crime, especially reported assaults, has increased in the area around the camps".

Image caption More than 100 tents were removed from the plaza on Monday

Using loudspeakers, police warned that anyone who resisted orders to leave the parks and surrounding areas risked arrest and "may also be subject to chemical agents and impact weapons".

Witnesses said there were confrontations and shouting as police in riot gear attempted to move people out of the squares.

Meanwhile, a group of small-business owners in New York on Monday urged the authorities to put an end to the original Occupy Wall Street camp in Zuccotti Park.

They said it was ruining their businesses and complained that protesters kept using their toilets facilities to wash, deterring customers.

The owner of a Chinese restaurant said demonstrators had been disposing of bags of their excrement outside his business.

The New York camp is due to mark the beginning of its third month of continuous protest on Thursday.

In St Louis, Missouri, where 27 anti-Wall Street protesters were arrested on Saturday, lawyers for Occupy St Louis planned to take their bid to regain their downtown campsite to federal court on Tuesday.

Police also moved in to evict protesters camping in the cities of Denver, Colorado, and Salt Lake City, Utah, on Saturday. Seventeen people were arrested in Denver, police said.