At least 13 people have been killed during a police operation in a slum near Rio de Janeiro, including the leader of a drug-trafficking ring active in northern Brazil, authorities said.

Rio de Janeiro police spokesman Fabricio Oliveira told a news conference on Thursday: "There are 13 dead, two people have been arrested and a large quantity of weapons confiscated."

Police said earlier in a statement that the operation at the Salgueiro complex in São Goncalo, a poor suburb of Rio, was aimed at arresting "members of the Vermilio commando from the northern state of Pará who took refuge in the area."

Commando Vermilio is one of Brazil's oldest and largest crime gangs, focused on drug trafficking.

Oliveira added that "it was very violent" by what he described as "a gang that uses military tactics and guerrilla warfare". The police spokesman said two women were wounded during an intense shootout but were "not in danger".

Among those killed was "Leonardo Araujo, codenamed L41+, wanted by the police," "the main leader of the largest criminal organization operating in Pará," the governor of this northern state, Elder Barballeo, said on Twitter.

According to police, the organization he led was "mainly responsible for the deaths of 40 policemen since 2021" in Pará.

Police said the security operation was also targeting other gang leaders "involved in recent attacks in informal settlements in the western region of Rio", where cars were set on fire on Wednesday.

Amnesty International Brazil criticised the state government of Rio de Janeiro for the operation, which ended in a "bloody catastrophe", noting that "suburban, slum and black residents will have to endure the police-led war policy in Rio".