Police on Thursday seized machine guns and other military-grade weapons from a drug gang operating here in Brazil's second-largest city, authorities said.

The arsenal, which includes three combat rifles, 12 shotguns, four machine guns and a large-caliber pistol, was found in Dendê, a "favela," or shantytown, on Rio de Janeiro's north side.

Dendê is among the favelas that have yet to be "pacified," a process that entails an occupation by security forces to expel gangs and the establishment of permanent police outposts to ensure the drug dealers don't return.

The pacification campaign was launched as Brazil geared up to host the 2014 World Cup, which began June 12 and runs through July 13, and the 2016 Olympics.

Police were pointed to the arsenal in Dendê by an anonymous telephone tip.

Besides the guns, the officers confiscated 20 kilos of marijuana.

Rio's iconic Maracana stadium has already hosted several World Cup matches and is the venue for June 28 and July 4 quarterfinal contests as well as for the July 13 final. EFE