RIO DE JANEIRO — More than 3,000 police and soldiers backed by armored personnel carriers raced into Brazil’s biggest slum before dawn Sunday, gaining control of a slum long ruled by a drug gang.

The takeover of the Rocinha neighborhood was the most ambitious operation yet in an effort to increase security before Rio hosts the final matches of the 2014 World Cup and the 2016 Olympics.

The head of state security and chief architect of Rio’s shantytown pacification program, Jose Mariano Beltrame, called the operation a major success and a big step toward breaking drug traffickers’ hold on key parts of Rio.

“We have taken over areas that for 30 or 40 years were in the hands of … a parallel power,” he said. “It’s one of the biggest shantytowns in the Americas if not the world. We’re returning dignity and territory to people.”

The action in Rocinha is part of a campaign to drive the drug gangs out of the city’s slums.

Authorities said it took just 90 minutes to seize control of Rocinha. Police simultaneously overran the neighboring Vidigal slum, also previously dominated by the Friends of Friends drug gang.

Both slums sit between two of Rio’s richest neighborhoods. Police methodically cleared alleys and streets on their way up steep, winding roads.

Huey helicopters swarmed over the slum, crisscrossing the hill and flying low over the jungle surrounding the slum, as police hunted down suspects who might have fled into the forest. By evening, police said they made just four arrests.

Police discovered a house they said belonged to the No. 2 gang leader, Sandro Luiz de Paula Amorim, known as “Peixe,” who was captured by police when they encircled Rocinha with roadblocks.

In stark contrast to the impoverished shacks around it, Amorim’s three-story home was outfitted with a large whirlpool bath, swimming pool, aquarium, high definition TV and a book: the ancient Chinese military text “Art of War.”

A resident applauded the police. “Tell the world we’re not all drug traffickers! We’re working people and now they’re coming to liberate us,” a man yelled at police.