RIO DE JANEIIRO - Shoot-outs between drug gangs left at least six people dead over the weekend in two Rio de Janeiro favelas, the latest in a flare-up of violence in recent months.

Through much of Sunday morning, heavy exchanges of gunfire terrorized residents of Rocinha, Rio's biggest favela with 75,000 inhabitants.

Nearly a quarter the city's 6.45 million population live in favelas, the term Brazilians give for the poor, densely populated neighborhoods clustered on the city's steep hillsides.

"Clashes between traffickers in Rocinha. Avoid the area," Rio's military police warned on the force's Twitter account.

Local security services told AFP that one person was killed in Rocinha on Sunday, the day after five other people were killed in neighborhoods north of the city.

Witness accounts on social media indicated more than one person may have been killed in Rocinha, and several videos showed armed men running through the neighborhood's maze of alleys.

Several helicopters overflew the area and entrances to a metro station at Sao Conrado -- a wealthy neighborhood in southern Rio below Rocinha -- was closed for several hours.

Police also were attacked in the early morning by a group of heavily armed men near the favela, according to the authorities.

A police source told AFP that they suspect the violence was due to internal divisions in the gang that controls drug trafficking in Rocinha.

According to local media, members of the same gang were behind clashes that left five dead overnight Friday to Saturday in Morro do Juramento, a favela north of Rio.

Firefighters confirmed that they recovered five bodies from that area, while the local press put the toll there at seven dead.

Rio has seen deadly violence spiked during the first half of the year to its highest level since 2009, with 3,457 homicides, a 15 percent jump from the same period last year, according to the Public Security Institute.

The growing sense of insecurity has been aggravated by the state of Rio's dismal financial situation. On the verge of bankruptcy, it is a month behind in payments of wages and salaries to its workers, including the police.

The government has turned to the army to combat the upsurge in violence, deploying nearly 10,000 troops at the end of July.

They have already taken part in two huge operations against the armed gangs in the city's favelas.

The newspaper O Globo, however, reported that the military has not taken part in the last two operations led by local authorities and the troops may soon be pulled out of the city.