Police raided gang-ruled shantytowns and said 10 suspected criminals died in gunbattles on Wednesday as authorities tried to halt a wave of violence that has rattled rich and poor alike in a city Brazil hopes to make a showplace for the 2016 Olympics.

Police invaded the Vila Cruzeiro and surrounding shantytowns early Wednesday, engaging in intense gun battles. Ten men died and one was arrested. Officers seized weapons including a grenade and an automatic rifle.

A police spokesman said at least four buses and 10 cars were burned in Rio's poorer northern and western areas overnight _ bringing the total to 22 attacks and 23 burned vehicles since Sunday.

One officers was reported hurt and one civilian was killed resisting armed robbers.

Schools in violence-struck areas saw low attendance Wednesday as worried parents kept children at home.

Gangsters armed with assault rifles and grenades used cars to block major thoroughfares, then robbed people snarled in the resulting gridlock and set some cars ablaze, sending black smoke billowing into the sky.

Security officials say the gang attacks aim to force authorities to stop a campaign to force gangs out of shantytowns where they have long ruled with impunity.

Thirteen shantytowns have been pacified over the past two years. The plan is to free 40 _ a small fraction of Rio's more than 1,000 slums _ of gang control by the time of soccer's 2014 World Cup.

Police said a note found on one of the burning buses Wednesday warned that if law enforcement continues to push drug dealers out of the slums, Rio won't be able to host the Olympics.

Rio state Public Safety Director Jose Beltrame said security forces will not be deterred.

"This is not an easy task, but it is also an opportunity to build a better city," Beltrame told Globo TV Wednesday. "We are not giving back one millimeter. Their threat shows we are on the right path. They're being affected."

Rio's governor, Sergio Cabral, urged calm.

"What the bandits want is panic," he told CBN radio Wednesday. "We are facing a desperate reaction from criminals. But we are not going to despair."

Police have responded to the attacks by deploying riot officers on expressways into the city of 6 million people and sending patrols into more than 20 gang-controlled shantytowns to hunt down gang members they hold responsible for the attacks.

Violence has plagued Rio for decades, but most has been contained within the slums that cling to the hillsides. Now, however, at least a few of the recent attacks have spilled into middle class and wealthier neighborhoods closer to the beach, spreading fears that police are losing control of the city.

"The scary part is that now it's getting close to us. Before the violence was always far away," said Olga Silveira, who was milling around a plaza in the wealthy Ipanema neighborhood where police blew up a large, empty wooden box mistakenly feared to contain explosives. "Now we're feeling it on our flesh. The criminals have discovered the power they have and they want to show it."

Reginaldo Maciel, a police officer patrolling Ipanema, said the box started attracting attention around 7 a.m. Traffic was halted for several hours on a few streets around the plaza _ causing havoc for morning commuters trying to travel through the neighborhood, whose streets are a traffic choke point.

___

Associated Press writer Bradley Brooks in Sao Paulo contributed to this report.