Brazil violence: At least 18 killed in police raid on Rio favela

Police in Brazil say 18 people have been killed during a raid against a criminal gang that controls one of Rio de Janeiro's most violent favelas.

Four hundred heavily-armed military police were deployed to the Alemão favela in the early hours of Thursday.

Sixteen of the dead were suspected criminals, while a police officer and a bystander were the other two victims, officials said.

The operation lasted all day and left thousands trapped in their homes.

The objective of the raid was to locate and arrest criminals who were planning operations in rival slums, police said.

Some of the targets were wearing uniforms similar to military police, which made them harder to spot, local media outlet O Dia reported.

The 400 officers were backed up by 10 bullet-proof vehicles and four helicopters.

Locals were seen carrying injured people into vehicles as police watched.

Gilberto Santiago Lopes, from the Anacrim Human Rights Commission, said police refused to help.

The police "don't aim to arrest them, they aim to kill them, so if they're injured, they think they don't deserve help", he told Reuters.

Deadly raids are not uncommon in Rio de Janeiro's favelas, as police seek to hunt down drug trafficking gangs.

But human rights groups in Brazil are highly critical of police operations in overcrowded, low-income communities, saying they put the lives of residents at risk without really curbing the power of the gangs.

In May, 22 people were killed, also including a female bystander, in the Vila Cruzeiro favela.