Brazilian security forces backed by helicopters and armoured vehicles have raided two favelas near Rio de Janeiro's international airport.
More than 1,300 elite police commandos and marines swooped on the drug gang strongholds of Caju and Barreira do Vasco.
Within three hours, security forces retook control of the streets and hoisted the flags of Brazil and Rio to proclaim the reinstatement of authority to the neighbourhoods.
No shots were fired. Rio de Janeiro's state secretary of public security José Mariano Beltram described the mission as a success.
Sixteen suspects were arrested and police seized two rifles, a shotgun, a gun, a large number of ammunition and small quantities of crack cocaine, marijuana and a chemical drug known as "Lolo".
The raid was part of the "pacification" programme to oust criminal gangs from 40 favelas and secure the country's most dangerous areas ahead of the 2014 World Cup and 2016 Olympics.
Thirty favelas have been raided since the programme was launched in 2008. Rio has more than 600 shantytowns.
Critics say the operations target only areas near tourist neighbourhoods and fail to tackle the underlining problems, as criminals are tipped off and flee ahead of police intervention to resurface elsewhere.
"Some people say the result [of the operation] is frustrating because there were few arrests," Beltram told Jornal do Brasil newspaper.
Beltram said police pressure on Caju and Barreira do Vasco over previous months had led to more than 200 arrests.
"Occupying an area without firing a shot is a success. The policy of pacifying has to be done this way," Beltram said.