The International Olympic Committee (IOC) insists security at the Rio 2016 Games will not be compromised following a spate of attacks against police in the city's slums.
A police officer was shot in the leg during the latest outbreak of violence involving drug dealers in the Manguinhos favela, or shanty town, Thursday, reports Xinhua.
Four policemen have been shot dead since February in clashes with gangsters in Rio's favelas.
The head of the IOC's Evaluation Commission, Nawal El Moutawakel, admitted on Friday the incidents were cause for concern.
"I was told about what happened," El Moutawakel said during a press conference following a visit to Rio's Olympic Park.
"It's very sad. Security is always a priority for us," she said.
Her comments came as the governor of Rio de Janeiro state, Sergio Cabral, sought federal support to quell the unrest.
Local newspaper Folha de S Paulo reported on Friday that President Dilma Rousseff had mobilised the nation's armed forces to re-establish order in some favelas.
The escalating violence has renewed concerns about Brazil's ability to guarantee security during this year's FIFA World Cup and the 2016 Olympics.
Rio will host seven World Cup matches, including the final July 13.