Updated

Brazilian authorities raided gang-ruled shantytowns in Rio de Janeiro on Wednesday in an effort 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 in northern Rio de Janeiro and surrounding shantytowns early Wednesday. Gun battles resulted in the deaths of 10 suspected criminals. 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.

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

Thirteen shantytowns have been pacified by police 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 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 José 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."

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."

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