Youths roamed the cobblestone streets of Oaxaca tossing gasoline bombs, hijacking vehicles and vowing to keep fighting for the state governor's ouster. Mexico's Congress urged the governor to resign and leftist leaders urged national support for the movement.

Thousands of protesters also faced off with police Monday outside the city's central main plaza, screaming "Murderers! Murderers!" as they lit fires and tossed Molotov cocktails and fireworks toward the police lines.

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There were no direct clashes between the two sides. One officer was taken to the hospital after being hit by fireworks.

The demonstrators were driven from the central plaza, the Zocalo, on Sunday after President Vicente Fox sent in federal police backed by armored vehicles and water cannons. They peacefully occupied another nearby plaza where they planned to set up their new base.

The protest began in May as a teachers' strike but quickly spiraled into chaos as anarchists, students and Indian groups seized the central plaza and barricaded streets throughout the city to demand Oaxaca Gov. Ulises Ruiz's ouster.

The Mexican Congress passed a nonbinding resolution on Monday asking Ruiz to resign, while Zapatista rebel leader Subcomandante Marcos and former leftist presidential candidate Andres Manuel Lopez Obrador called demonstrations in other Mexican cities to support the demonstrators.

The U.S. Embassy, meanwhile, released a statement advising Americans against all travel to one of Mexico's top tourist destinations "due to this increase in violence."

Ruiz, who protesters accuse of rigging 2004 elections and oppressing dissent, has refused to step down and accused "radical groups" from Mexico City of fueling the street battles in Oaxaca.

Ruiz on Monday returned to offices he had been forced out of months ago by the protesters. But police control of the city remained only partial at best; new barricades sprung up on the road to his offices in a matter of hours after police had cleared the way.

Armored trucks with water cannon posted at the edges of the main plaza fired jets of water to extinguish blazes set by the protesters. Officers fired occasional rounds of tear gas in answer to the gasoline bombs and powerful fireworks that protesters launched at police lines.

Fox, who leaves office Dec. 1, had resisted repeated calls to send federal forces to Oaxaca until gunfire killed a U.S. activist-journalist and two residents on Friday.

On Monday, Fox said social order and peace had been "restored" in the city.

However, strike-weary residents saw their hopes for a return to normality dashed once again; schools in the city remained closed, despite a promise by teachers to return to work. A scattering of businesses, including some stalls in the city's famous marketplace, reopened Monday. There was little business.

Thousands of leftists and teachers marched through the city chanting, "Fight, fight, fight! Don't stop fighting!" before confronting police guarding the main plaza.

Ignoring protesters who screamed "Sellout!" a group of about 20 residents and business owners waged earlier countermarches to thank federal police for clearing away the demonstrators, who had kept the city under siege for five months, shutting down businesses and repelling the scores of national and international tourists who traditionally are drawn to the colonial city of 275,000.

"Let them stay," Edith Mendoza, a 40-year-old housewife, said of the police. "We were held hostage for five months."

Federal officials said the police would stay here as long as needed to restore order, but there did not appear to be enough of them to do the job.

Eight people have died in clashes since the protesters took over the city center. Protesters claim that police and state forces — often in plainclothes — have shot at protesters, setting off the violence. Among those killed was U.S. activist-journalist Bradley Roland Will, 36, of New York. Protesters say local police shot him.