Brazilian authorities did not detail their plans early Saturday, but it appeared security forces were preparing to invade the Alemao complex, a group of more than a dozen of Rio’s most menacing slums.

About 800 soldiers began providing support Friday for a police offensive that the previous day saw officers take back control of a nearby slum where gangs had held sway for decades. Authorities began raids on slums after a surge of gang violence broke out Sunday.

“Sooner or later, we’re going to get these criminals,” Rio state Public Safety Director Jose Beltrame told the Globo television network Friday night. “The anguish of Rio’s citizens is my anguish. But we have our objectives and we cannot retreat.” Brazilian officials are also concerned about the image of the city that will be host for the final match of the 2014 World Cup and Summer Olympics in 2016.

Military spokesman Enio Zanan said that soldiers came under fire from drug gang members hiding in the large Alemao complex, but that the troops were not shooting back because it endanger “innocent people in the community.” AP Television News video, however, showed at least one soldier firing his assault rifle at the slum, and the newspaper O Globo reported heavy exchanges of gunfire between troops and gang members.

Police said at least 32 people — mostly suspected drug gang members — had been killed in the battles since Sunday.

Beyond the deaths, basic services such as mail delivery and retail were disrupted as workers stayed home out of fear, or because bus companies kept vehicles off the roads for safety reasons. Many schools remained closed on the city’s poorer north side, where many slums sit.

Trains connecting the suburbs to the city had 10,000 fewer riders Friday morning, according to SuperVia, the company operating them.

Bars and restaurants emptied out all over town. The number of customers plunged 60 percent from usual levels, according to a statement by SindRio, which represents eateries and hotels.

Trash collection was suspended in the conflict zone and electricity was still out, the result of damage to cables during clashes between police and gunmen. The waste management company, Comlurb, and Light, which delivers electricity, issued statements saying it wasn’t safe for their workers to enter the slums.

While gunfire rattled in Alemao, federal and state police conducted door-to-door searches and patrols in the nearby Vila Cruzeiro slum. That area was seized by officers Thursday during a five-hour operation using armored vehicles and assault rifles.

After police armored cars had their tires blown out by gangs or were stymied by burning tires, police relied on military armored personnel carriers equipped with caterpillar treads to roll over or push aside barriers and enter the fortified shantytown.

Officials trumpeted their success in Vila Cruzeiro, hailing it as a sign of a new Rio.

The governor of Rio state, Sergio Cabral, said the moment was historic — proving that no part of Rio is beyond the reach of the law. He also hailed the cooperation of the armed forces with police to bring peace to Rio, a city infamous among Brazilians for the violence of its lawless shantytowns.

“We have demonstrated to those who don’t respect the law ... the pre-eminence of a democratic state governed by the law,” he said. “Bringing peace to this population makes this a very important day for Rio.” Nearly 200 people have been arrested or detained since the start of the widespread violence Sunday, police spokesman Henrique de Lima Castro Saraiva said. More than 96 buses and cars were burned on major roadways, many motorists robbed and police outposts have been attacked.