Portland officials have issued a warning to the protesters of Occupy Portland after a police officer was shoved against a bus during an unruly march this week, and the police chief ordered his department to have riot gear at the ready.

Chief Mike Reese's orders came after protesters marched Wednesday in a demonstration that revealed a rift between radicals seeking confrontation with authorities and others in the movement who want a more peaceful approach. One person was arrested, accused of shoving an officer against a moving bus. The officer wasn't seriously injured.

Reese's order went out Thursday, and the text was made public on Friday. The order said that starting Friday, all police officers are required to have gas masks, batons, and helmets "immediately available" and be "prepared to deploy" with the equipment "in a timely manner."

Mayor Sam Adams said: "Violence like this will not be tolerated."

Protesters have been camped out in tents and under tarps in adjacent downtown parks since Oct. 6, and tensions surrounding the camp have risen in the past week.

Last Sunday, a large group of protesters marched from the camp to another public park in Portland's affluent Pearl District, despite city officials' warning they would not be allowed occupy it. Twenty-seven of the protesters were arrested after they refused to obey a midnight curfew.

On Tuesday, police removed several tents that had been set up on yet another park _ this one on federal land _ and detained nine people.

Tensions came to a head on Wednesday, when a sizeable contingent of protesters staged an unpermitted march through the city, the same day as a high-profile demonstration in Oakland, Calif. A splinter group of about 100 then marched across one of the bridges crossing the Willamette River, spilling onto the road as police tried to keep traffic flowing. That's when a police officer was shoved against a moving bus.

The patience of city officials is growing thin.

In Reese's email to his officers, he said the tone of the Wednesday march "seemed to change from previous events, and many in the crowd seemed confrontational _ provoking motorists and police."

He said because of the rain falling that night and limited visibility, marchers "posed a significant threat to themselves, police and motorists."

Although the sergeant who was pushed into a bus did not sustain serious injuries, it "could have been something far more serious," he said.

The Portland police union was blunt in its response to the Wednesday march, issuing a press release with the headline "Enough is Enough."

"We believe in, and support, the rights of citizens to free speech, including the right to protest and march, as long as it is within the confines" of the law, said Daryl Turner, president of the Portland Police Association.

He said Portland police officers have worked long hours and "shown great resolve."

"Now, Portland Police officers are being assaulted and threatened," he said.

He called on Portland residents who are having to make sacrifices because of Occupy Portland to let city officials know about it.

In its own press release, Occupy Portland said it condemned violence and that the protester who pushed the officer into the bus was "previously unknown to the encampment."

Organizers have acknowledged there are radicals who have attached themselves to the movement, are intent on trying to provoke police, and are a threat to the movement's message.