Brazil ? Hundreds of police agents swooped in on drug gangs in two Rio de Janeiro shantytowns on Wednesday, setting off gunbattles that killed 12 people, including an officer and a 4-year-old boy, officials said.

About 400 police officers, including members of elite units, entered the sprawling Coreia and Senador Camara slums to search for weapons and serve arrest warrants, said a police spokesman who declined to be identified according to department policy.

Intense gunfire broke out between police and alleged drug members as authorities staged the raid in broad daylight. Television news footage showed a police helicopter flying over the area and people running for cover as agents opened fire from atop a hill. One woman sought shelter from the hail of bullets by cowering behind a concrete wall, clutching a child.

Eleven suspected gang members were arrested, and police seized a machine gun, rifles, pistols, grenades, ammunition, cocaine and marijuana, according to Globo TV’s G1 Web site. Police said 10 of the dead were drug traffickers.