Anti-Wall Street protesters and their supporters flooded a city park area in Portland early Sunday in defiance of an eviction order, and authorities elsewhere stepped up pressure against the demonstrators, arresting nearly two dozen.

Crowds converged on two adjacent downtown Portland parks where protesters decrying economic injustice are camped after city officials set a midnight Saturday deadline to disperse. Hours later, protesters remained though by dawn Sunday the crowd had thinned and obeyed police orders to clear the street.

At one point overnight, the crowd swelled to thousands.

Organizers said they hoped enough people will join them to make it difficult if not impossible for police to carry through on any eviction.

"Occupy the street," one organizer said through a bull horn. "Remain peaceful and aware. We have strength in holding the streets."

Demonstrators had used pallets and old furniture, wood debris and even a bicycle to set up makeshift barricades on either end of a street that runs through the encampment, apparently in an attempt to block traffic. The barricades later were taken down by protesters.

Mayor Sam Adams had ordered the camp shut down, citing unhealthy conditions and the encampment's attraction of drug users and thieves.

On Sunday at an impromptu news conference, he defended his order, saying it is his job to enforce the law and keep the peace. "This is not a game," he said.

He also noted that implementing the eviction order may require more patience.

Police numbers shifted throughout the night, but they showed no signs of moving against the protesters. Around 4 a.m., a line of about 200 police stretched across a street and in front of a federal courthouse. Protesters facing them appeared to be in a festive spirits with some banging on plastic pails, while others danced in the streets as a man juggled nearby.

Officials said that one officer suffered minor injuries when he was hit by some kind of projectile in the leg.

Police had prepared for a possible clash, warning that dozens of anarchists may be planning a confrontation with authorities. Officers seized pieces of cement blocks Friday, saying they were told some demonstrators had plans to use them as weapons against police.

It appeared earlier that about 200 campers planned to get arrested. But police action seemed less likely after the crowds swelled the parks in the early morning.

In the hours leading up to midnight, protesters held general assembly meetings where they talked about what to do when the deadline came. They also repeated the main message of the Occupy Wall Street movement of peaceful resistance to income inequality and what they see as corporate greed.

As those speeches were going on, about 60 bicycle riders circled the camp repeatedly to show support.

"We are a peaceful resistance," said rider Chico Tallman, a 63-year-old accountant. "But we're fed up with the direction the country is going. It's all about profit."

On Saturday, Occupy Portland protesters dismantled large sections of their encampment, but dozens of tents remained after midnight.

For the second time in as many days, Oakland city officials warned protesters Saturday that they do not have the right to camp in the plaza in front of City Hall and face immediate arrest.

The eviction notices come as officials across the country urged an end to similar gatherings in the wake of three deaths in different cities, including two by gunfire.

Demands for Oakland protesters to pack up increased after a man was shot and killed Thursday near the encampment site.

"Your activities are injurious to health, obstruct the free use of property, interfering with the comfortable enjoyment of [Frank Ogawa Plaza], and unlawfully obstruct the free passage or use of a public park or square," the notice read.

Oakland officials first issued the eviction notice Friday after first pleading with protesters to leave the encampment.

Police officials have said a preliminary investigation suggested the shooting resulted from a fight between two groups of men at or near the encampment. Investigators do not know if the men in the fight were associated with Occupy Oakland, but protesters said there was no connection between the shooting and the camp.

The shooting occurred the same day a 35-year-old military veteran apparently committed suicide in a tent at a Burlington, Vermont, Occupy encampment. Police said a preliminary investigation showed the veteran fatally shot himself in the head. They said the death raised questions about whether the protest would be allowed to continue.

In Salt Lake City, police arrested 19 people Saturday when protesters refused to leave a park a day after a man was found dead inside his tent at the encampment. About 150 people had been living in the camp there for weeks.

Authorities in Denver forced protesters to leave a downtown encampment and arrested four people for interfering with officers who removed illegally pitched tents, said police spokesman Sonny Jackson.

Violence marked the protest in San Francisco Saturday where police said two demonstrators attacked two police officers in separate incidents during a march.

Police spokesman Carlos Manfredi said a protester slashed an officer's hand with a pen knife while another protester shoved an officer, causing facial cuts. He said neither officer was seriously hurt, and the assailants couldn't be located.

Meanwhile, in Southern California a small group of protesters braved soggy weather on Saturday to gather for the first time under the banner of Occupy Inland Empire, The Sun newspaper reported.

Associated Press writers Terry Collins in Oakland, Josh Loftin in Salt Lake City, Jim Anderson in Denver and Andrew Dalton in Los Angeles contributed to this report.