(Updates figure on number of homeless, details)

By Luis Manuel Lopez

VILLAHERMOSA, Mexico, Nov 2 (Reuters) - Thousands of people fled a Mexican city on Friday after flood waters burst through sandbag barriers in a disaster that left 800,000 people homeless and most of the state of Tabasco under water.

One person has been killed in the worst flooding the low-lying, swampy state has seen in more than 50 years.

The Grijalva River, which winds through state capital Villahermosa, swelled over its banks earlier this week after days of heavy rains.

People and livestock swam through the streets on Friday after a murky, brown deluge surged into Villahermosa, home to about half a million people.

Hungry and thirsty residents stood in long lines at supermarkets, although some stores closed after running out of food, water and medicine.

"There isn't much on the shelves and what is left is very expensive," said Juan Pablo Rosas.

The army evacuated most of the city center on Thursday night after a levee broke despite being piled with thousands of sandbags by army troops and volunteers.

"We were fighting against a monster," said Tabasco state Gov. Andres Granier.

President Felipe Calderon said Mexico's entire air force was engaged in an airlift to ferry supplies into Villahermosa and get residents out. He called on private airlines to help.

"We are in a critical situation," Calderon said during a visit to the region.

He said army troops and federal police would soon be patrolling the streets to prevent looting and price gouging.

The Red Cross in Mexico said on Friday the disaster has made 800,000 people homeless.

GOVERNMENT SURPRISED

Interior Minister Francisco Ramirez acknowledged the disaster took the government by surprise.

"The event overwhelmed everyone and that's why we all have to work intensely," he said. The city center was under between 6 1/2 feet (2 meters) and 19 feet (6 meters) of water.

Rescue workers broke windows of homes to reach stranded residents. Thousands fled in military helicopters or private trucks.

"When will this finish?" said resident Maria de la Luz Robles. "This is chaotic and depressing."

Gov. Andres Granier said more than 1 million people, about half of the state's population, were affected by the flooding. Scores called local radio programs pleading to be rescued. Many shelters were evacuated after floodwaters overtook them.

Navy helicopters rescued scores of people on Friday morning from the village of El Aguacate. They had gathered on a tiny plot of high land as flood waters rose around them.

Water half-covered several giant carved stone heads built by the Olmecs, the mother culture of Mesoamerica, at Tabasco's La Venta archeological site. Some of the heads are more than 9 feet (3 meters) tall.

The floods were triggered by storms that have wreaked havoc in the oil industry along Mexico's Gulf coast but the main oil port of Coatzacoalcos opened on Friday after closing earlier in the week due to the bad weather.

(Additional reporting by Jason Lange in Mexico City)

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