In a separate incident on Wednesday, an officer was wounded in a gun battle with drug-traffickers who have maintained their bases in the Vila Cruzeiro shantytown despite a police occupation that has lasted more than a month.
Seventeen people have been killed and 57 have been wounded in Vila Cruzeiro since the start of May, most of them innocent residents hit by stray bullets during police raids with the support of armored vehicles.
Human rights groups such as Amnesty International accuse Rio police of being excessively violent during raids and even of resorting to summary executions of suspects.
The Rio authorities have said they plan more slum occupations before the July 13 start of the Pan American Games as they try to reduce security concerns at the event in a city with one of Latin America's highest murder rates.
More than 1,300 people were murdered in the Rio metropolitan area in the first three months of the year, according to official data. Police killed 303 suspects in the same period.