RIO DE JANEIRO (Reuters) - At least five civilians and one soldier died in shootouts in northern Rio de Janeiro on Monday, the army said, as thousands of Brazilian soldiers swept into slums in pursuit of drug gangs, trapping terrified residents in their homes.

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Separately, at least six suspected gangsters were killed on Monday near a bridge linking Rio and the neighboring city of Niteroi, police said. Four people died in the shootout with police, while two more died in hospital.

The army said the early-morning raids took place in several of the city’s most violent neighborhoods, which are home to more than half a million people and have been targeted in a divisive six-month federal security operation.

Initially, the army had reported eight people were killed. It later lowered the death toll, and said two soldiers were injured, with one dying from his injuries.

“The operations are ongoing and there could be more deaths,” the army said in an email to Reuters.

Many people shut themselves inside their homes for fear of being shot if they went outside, the Globo TV website reported.

The joint army and police operations, which the army said were intended to flush out drug dealers, involved 4,200 soldiers and 70 police, as well as armored vehicles and aircraft.

The soldier who died on Monday was the first to be killed since the intervention began, the state security ministry said.

Just over six months ago, President Michel Temer announced emergency measures authorizing the army to take command of police forces in Rio de Janeiro state, where warring drug gangs and militias have triggered a sharp rise in violence.

Since the operation began, both murders and the number of people killed in police confrontations have risen, casting doubts on a strategy criticized for relying on military tactics, a lack of transparency and unclear goals.

Nearly 64,000 people were murdered in Brazil in 2017, a record high, and the rise in violence has become a key issue ahead of presidential elections in October. Candidates across the political spectrum are trying to play up their crime-fighting credentials and appeal to an electorate fed up with a weak economy and endemic graft.