A bus on fire sits at Jacarezinho slum after being burnt by alleged gang members Saturday in Rio de Janeiro. Gun battles raged in the northern Rio slum after midnight in clashes between rival gangs, and a police helicopter was forced to land in a soccer field after the pilot was shot in the leg. The pilot and three other police officers who were in the helicopter escaped the area after landing.

Rio de Janeiro ? Drug traffickers shot down a police helicopter during a gunbattle between rival gangs Saturday, killing two officers and injuring four in a burst of violence just two weeks after the city was chosen to host the 2016 Olympic Games.

Ten suspected drug traffickers were also killed during the fighting in a shantytown, along with two bystanders in the slum, officials said.

Bullets flying from the Morro dos Macacos (“Monkey Hill” in Portuguese) slum in northern Rio de Janeiro tore into the helicopter and hit the pilot in the leg as he hovered above the shootout, causing him to lose control and crash.

Two officers died, while the pilot and three other policemen escaped after the craft hit the ground on a football field and burst into flames. The pilot and a second officer suffered burns and bullet wounds. The other two officers also were burned, one gravely, said Mario Sergio Duarte, head of Rio state’s military police.

Officials did not know whether the gangs targeted the helicopter or whether it was 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 soccer tournament 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,” Justice Minister Tarso Genro told the state-run Agencia Brasil news agency.

Rio state Gov. Sergio Cabral grimly told reporters that Rio’s security challenges can’t be cured “by magic in the short term,” but he said money is being poured into programs to reduce crime and authorities are prepared to mount an overwhelming 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,” Cabral said. “We can put 40,000 people on the streets — federal, state and municipal police — and pull off the event.”

Duarte said it was unlikely that traffickers fired an anti-aircraft missile at the helicopter, though 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-caliber machine guns.

The pilot was able to make a somewhat controlled, though extremely rough landing, which would have been unlikely if the aircraft had been hit by a heavy weapon, Duarte said.

Police said 10 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 at least eight buses were set on fire in nearby slums as the shootouts raged. Television images showed motorists fleeing for cover as automatic-weapons fire crackled in broad daylight amid the worst violence the city has seen in months.

Images broadcast by Globo TV showed flames shooting from the helicopter wreckage, with little more than charred pieces and an intact tail remaining after the fire was doused.

Rio police frequently use helicopters to take on 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 one of their helicopters had been shot down by gang members.

The crash happened about five miles southwest of one of the zones where Rio’s 2016 Olympics will be located. The city on Oct. 2 was picked over Chicago, Madrid and Tokyo to host the games. Rio alone among the bid cities 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.