A bus on fire sits at Jacarezinho slum after being burnt by alleged gang members in Rio de Janeiro.(AP)

RIO DE JANEIRO (AP) — 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, and two bystanders were injured, 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.