Brazil - At least 21 people were shot dead in a slum on the north side of Rio de Janeiro on Tuesday during a police raid to capture the leaders of a drug-trafficking organization, police and hospital officials said.

The deaths included a woman who was hit in the exchange of gunfire between gang members and police in the Vila Cruzeiro favela, as Rio slums are called. Police said the other dead were suspected gang members who resisted the enforcement operation and opened fire on police with automatic weapons.

Residents said that heavy shooting began in darkness at 4 a.m. in a wooded area next to Vila Cruzeiro, sparking fear and panic in the slum. Gunfire began again in the afternoon.

Seven wounded people were taken to hospital, including a policeman.

The police operation, backed by a helicopter, targeted leaders of Rio's largest organized crime gang, the Comando Vermelho, who, according to police intelligence, were hiding in Vila Cruzeiro.

"It was a very intense confrontation," Colonel Ivan Blaz, spokesman for the militarized police force that led the operation, told reporters. He said the woman could have been hit by a shot fired from inside Vila Cruzeiro.

Police seized assault rifles, pistols and a grenade, as well as cars and motorbikes used by the criminals, he said.

The dead woman was identified as 41-year-old G.C., hit by a stray bullet even though she lived in a neighboring slum called Chatuba. Schools did not open for classes.

Last year, 28 people died in violence in Rio slums, mostly in clashes between drug traffickers and police.