Drug traffickers shot down a police helicopter in a gun battle between rival gangs on Saturday, killing two officers, as the Brazilian city was engulfed in a renewed outburst of violence two weeks after winning its bid to host the 2016 Olympic Games.

Bullets ripped into the helicopter as it hovered over a shoot-out between police and drug traffickers in the Morro dos Macacos, or “Monkey Hill”, slum in northern Rio de Janeiro. The pilot was hit in the leg, causing him to lose control and crash.

Two officers died, while the pilot and three other policemen escaped after the aircraft hit the ground on a football field and burst into flames.

The pilot and an officer suffered burns and bullet wounds while the other two officers were burned, one seriously, said Mario Sergio Duarte, the head of Rio state’s military police.

Officials did not know whether the gangs had targeted the helicopter or whether it had been hit by stray bullets but the event underscored security concerns that have dogged Brazil’s second-largest city for decades.

Despite the mayhem, officials defended Rio’s ability to control violence ahead of the Olympics, as well as before 2014, when Brazil will host the World Cup, with key games in Rio.

“In choosing the city, they already knew about the work that’s being carried out and will continue in the area of [crime] prevention,” Tarso Genro, the Justice Minister, told the state-run Agência Brasil news agency.

The governor of Rio state, Sergio Cabral, told reporters that Rio’s security challenges could not be cured “by magic in the short term” but he said that money was being poured into programmes to reduce crime and that authorities were prepared to mount a vast security presence at the sporting events to ensure safety.

“We told the International Olympic Committee that this won’t be an easy thing and they know that," Mr Cabral said. “We can put 40,000 people on the streets — federal, state and municipal police — and pull off the event.”

Mr Duarte said that it was unlikely that traffickers fired an anti-aircraft missile at the helicopter, although such weapons have been found in the hideouts of Rio’s drug traffickers, along with other heavy, military-grade arms such as grenade launchers and .50-calibre machine guns.

Police said that ten presumed traffickers were killed during the fighting in the slum, including three suspects found dead inside a vehicle. Officials gave no details on how the other seven died.

They said that at least eight buses were set on fire in nearby slums as the shoot outs raged. Television images showed motorists fleeing for cover as automatic weapon fire crackled in broad daylight amid the worst violence that the city has seen in months.

Images broadcast by Globo TV showed flames shooting from the helicopter wreckage, leaving little more than charred pieces and a tail.

Rio police frequently use helicopters to take on the gangs that dominate drug trafficking in the city’s more than 1,000 slums, but were unable to say whether this was the first time that one of their helicopters had been shot down.

The crash happened about five miles (eight kilometres) southwest of one of the zones where Rio’s 2016 Olympics will be located. The city was picked over Chicago, Madrid and Tokyo on October 2 to host the games but it was highlighted for security concerns ahead of the International Olympic Committee vote.

The downing of the helicopter happened amid intense firefights involving rival gangs in the slum as one tried to seize a rival’s territory, authorities said.

Police moved into the area before dawn, although gunfire continued throughout the day, barricading terrorised residents inside their homes as bullets ripped into apartment buildings. Mr Duarte said late in the day that the areas were under control and television images showed people emerging into the streets at dusk.

Despite increased policing efforts, Rio remains one of the world’s most dangerous cities. The violence is generally contained within the slum areas, although it sometimes spills into beach neighborhoods and periodically shuts down the highway that links the international airport to tourist destinations.

Brazilian President Luiz Inácio Lula da Silva and other officials have played down the threat of violence for the Olympics, saying that Rio has repeatedly demonstrated that it can pull off big events without risk to players or spectators.

Rio held the Pan American Games in 2007 without major incident, deploying more than 15,000 specially trained officers to keep the peace.

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