LA PAZ, Bolivia (AP) _ Bolivia's president declared a state of emergency Saturday, sending police with tear gas and rubber bullets into the streets of the country's third-largest city to try to quell demonstrators who hurled rocks and Molotov cocktails back at them.

Three protesters were reported killed in separate clashes with police, and Government Minister Walter Guiteras said scores of protest leaders were detained and confined to San Joaquin, a remote town on the border with Brazil, 460 miles from La Paz.

The government's move came after a week of protests over rising water rates, unemployment and other economic difficulties plaguing this nation in the heart of South America.

It was the seventh time that such an emergency, which suspends many constitutional guarantees _ but is much less serious than a call for martial law _ has been imposed since democracy returned to Bolivia in 1982.

The days of protests were fueled Friday, when at least 800 elite police, firefighters and congressional guards staged a mutiny, barricading themselves in a police headquarters just a block from the presidential palace.

The police, who earn on average $80 a month, were demanding a pay raise. Thousands of students and other supporters gathered around the police headquarters to show solidarity with the mutineers.

Military police armed with machine guns used tear gas and rubber bullets to break up crowds of protesters in Cochabamba who threw rocks and Molotov cocktails at them. Tires were set on fire throughout Cochabamba. Several government office buildings, a fuel depot and vehicles were either stoned and set on fire.

Police in Cochabamba seized radio stations to prevent independent reporting on the situation.

The body of one victim, reportedly shot and killed by police on Saturday, was carried through the streets of the city, where thousands hailed him as a martyr.

By late Saturday, however, the situation in Cochabamba had calmed, with a strong police presence on the streets.

President Hugo Banzer claimed the protests in Cochabamba and road blocks throughout the country were threatening democracy. Food shortages were already being felt in La Paz and other cities.

``We find ourselves with a country with access roads to the cities blocked, with food shortages, passengers stranded and chaos beginning to take hold in other cities,'' Information Minister Ronald McLean said.

A state of emergency allows the government to arrest and confine protest leaders without a warrant, impose restrictions on travel and political activity and establish a curfew. It was called for up to 90 days.

Among those arrested, Guiteras told a news conference, was the leader of the country's main farmers' organization.

One protester was killed in Patacamaya, about 115 miles south of La Paz, while soldiers were clearing a roadblock. In nearby Lahuachaca another died from what Guiteras said was a heart attack, but witnesses said he was shot by soldiers. Both protesters were peasants.

The third victim was shot and killed by police in Cochabamba, according to witnesses.

Officials said an unspecified number of demonstrators were injured in the protests, none of them seriously.

The protests began over a 20 percent increase in water rates in Cochabamba, which is 350 miles east of La Paz. The government claims the increase is needed to fund the extension of supplies in a city that has suffered recurrent water shortages in recent months. Rates now average $30 a month _ 10 to 15 percent of average household income.

The protests quickly spread, eventually including police and teachers.

This is the first state of emergency declared by Banzer, a former dictator who has ruled Bolivia after he was democratically elected in 1998. The previous emergencies came after economic measures took effect that led to widespread protests in this country of eight million.