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RIO DE JANEIRO (Reuters) - A third Brazilian soldier, wounded in a sweeping operation this week targeting warring drug gangs in slums across Rio de Janeiro, has died, the army said on Wednesday.

At least five civilians and two soldiers died in the coordinated raids across violent neighborhoods in the north of the city on Monday, the army said at the time.

However, on Wednesday, authorities said a third soldier, who had been wounded in the raids, died of injuries that had initially been considered treatable.

The soldiers are the first troops to die in a six-month-old federal intervention in Rio, which has been criticized for military tactics, a lack of transparency and unclear goals.

In February, President Michel Temer announced emergency measures authorizing the army to take command of police forces in Rio de Janeiro state, where 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 the strategy, according to official data.

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 playing up their crime-fighting credentials to appeal to an electorate fed up with a weak economy and endemic graft.