More than 100 police officers in riot helmets shoved Occupy L.A. protesters off the streets in the Civic Center area of downtown Los Angeles today to clear the area for vehicular traffic, but they made only four arrests and made no move to dismantle their tent city, apparently saving that operation for another day.

A citywide Tactical Alert, under which officers scheduled to go home were kept overtime, was issued last night but canceled about 7 a.m. How much it cost cash-strapped Los Angeles was not immediately disclosed.

The Los Angeles Police Department announced shortly before 5 a.m. that demonstrators who were off the sidewalks and on the streets near City Hall represented an unlawful assembly and gave everyone five minutes to clear off, particularly at the intersection of First and Main streets on the south side of City Hall, in front of the Occupy L.A. encampment.

When the deadline expired, the officers -- moving in formation -- pushed the protesters, and some reporters, off the sidewalks and, briefly, onto the streets, then herded everyone into the Occupy L.A. encampment. The officers encountered little resistance.

Shortly after 6 a.m., lines of police motorcycles began riding up and down First Street. By 6:30 a.m. the roadway was cleared and open to traffic. Until then, Metro buses on about 20 lines were re-routed around the area overnight.

After the streets were cleared, LAPD officers armed with batons and weapons loaded with rubber bullets lined First Street and part of North Main Street on the flanks of the encampment, and field commanders barked out orders to tighten up the skirmish lines. Several demonstrators tried to engage the officers.

"How many of you have lost homes because of bank foreclosures?" asked one masked protestor. Another man urged the officers to join the movement of the "99 percent."

The officers remained impassive in the face of such entreaties. About 5:20 a.m., police led one man away in plastic tie handcuffs, and then another man and a woman.

LAPD Officer Rosario Herrera said four people were arrested for "failure to disperse." A woman was among the arrestees.

One man wearing a white clown mask and carrying a bullhorn climbed atop a traffic signal, delivering a tirade against police brutality and an impassioned defense of his First Amendment rights. But the crowd shouted at him: "Shut up. Get down, you don't speak for us."

About 5:30 a.m., several protesters started throwing signs and wooden stakes at the line of police officers at the corner of First and Main streets. But other protesters grabbed them and stopped things from escalating.

"No violence. No violence," several protesters shouted. "We are a nonviolent movement. The police are not our enemies."

The tension on the streets and in the encampment began to build throughout Sunday night after the city issued what was universally understood to mean that the protesters had until 12:01 a.m. to clear out of their tent city. Around midnight, the crowd inside the camp and on the streets grew to an estimated 4,000 people, according to some officers.

By daybreak, the crowd at the camp had dwindled to the hundreds. But almost all of tents remained standing and protestors were vowing to "hold the park."

Police Chief Charlie Beck told reporters this morning that the news media had misunderstood the significance of the 12:01 deadline. He said that's the time when living in the encampment became unlawful, but when to take it down is left to his discretion and could take place tonight, Tuesday night or the following night.

LAPD Cmdr. Andy Smith said the department's "No. 1 objective" this morning was to keep the streets clear rather than to dismantle the encampment.

"Our goal right now is to try and keep it as peaceful as possible," said Smith.

For more stories from KTTV in Los Angeles go to myfoxla.com.

Follow us on twitter.com/foxnewslatino
Like us at facebook.com/foxnewslatino