Photos of a gun battle in a Rio de Janeiro favela between 400 police and armed suspected criminals

So far, the death toll sits at 18, which includes one police officer, 16 alleged criminals and a female bystander, police said.

Approximately 400 officers, four aircraft and 10 armored vehicles were sent to the raid the favela.

Brazil's public defender said "There are signs of major human rights violations, and the possibility of this being one of the operations with the highest number of deaths in Rio de Janeiro," Reuters reports.

The assault on the favela has sparked criticism of Rio's police force.

Writing on Twitter, Talíria Petrone, a federal lawmaker for Rio, said, "This failed public security policy leaves residents and police on the ground, en masse. It's no longer possible to keep piling up Black bodies and favela residents every day!"

Speaking to NPR, Robert Muggah, co-founder of Igarapé Institute, "The killings resulting from large scale police operations is a grim reminder that militarized policing is not only ineffective, it is counterproductive."

This raid is not the first of its kind, with Amnesty International Brazil stating that they are becoming common practice.

"We are halfway through the year and, practically every month, Amnesty International Brazil has gone public to repudiate massacres in favelas in Rio de Janeiro. This situation seems to indicate that Governor Cláudio Castro is using the massacres as a public security policy." Jurema Werneck, Executive Director of Amnesty International Brazil, wrote in a statement.

Rio de Janeiro needs to turn the page on this violence immediately," she added.

Residents of the favela protesting the police presence waved white sheets.

According to Associated Press, residents were walking through the favela carrying bodies as bystanders around them shouted, "We want peace!"

At the beginning of July, the UN released a report over police brutality in Brazil, saying, "We have repeatedly raised our concerns about the excessive and lethal use of force used by Brazilian law enforcement officials and the disproportionate impact on Brazilians of African descent.

However, the latest reports of police brutality appear to show that such human rights violations continue with impunity," the report says.

According to Brown University, young black Rio residents are more than twice as likely to be the victim of a homicide than white citizens of the same age group, with most of these killings being perpetrated by police.

The Washington Post reports that Rio police said the suspects dressed in military uniforms to confuse the police, blocked the roads, and used residents as human shields.

The police have defended their actions, with Ronaldo Oliveira, who handles operations for Rio police saying, "We chose the day and time to try our best and avoid conflict," the Post reports.

Gilberto Santiago Lopes, from the Anacrim Human Rights Commission, told Reuters that police refused to help the injured.

"We had to carry them away in a beverage truck and then flag a local resident in their car to take them to hospital," he said.

"[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."

Police violence and security have been — and continue to be — the subject of an intense debate in Brazil's upcoming general election, which will take place on October 2.

Jair Bolsonaro, Brazil's right-wing president who is seeking reelection, has previously said that criminals should "die like roaches."

The left-wing Brazilian Workers' Party has announced it has nominated Luiz Inácio Lula da Silva to run to lead Brazil. Commonly known as Lula, he led the country from 2003 to 2010.

Speaking last year, Lula said, "Many times, when police go [to favelas], they don't go to solve violence. They contribute. They bring in violence, as well," The Washington Post reports.