SAO PAULO (AFP) - Eight Brazilian military police officers were arrested on Monday as part of a probe into the murder of two youths after the fatal shooting was shown on television, the force said.

On Sunday, Globo TV aired a video of footage stemming from security cameras that shows two men on a motorcycle approach three youngsters in the popular Bras neighbourhood in Sao Paulo, without taking off their helmets, and shoot two of them.

Images from another camera show that, at the time of the executions, a military police vehicle was parked about 50 metres from where the victims were.

"We are working to find the third youth who was seen in the images and managed to flee," Civilian Police Director Elizabeth Sato told local media.

Sao Paulo, with more than 11 million people, is set to host 2014 World Cup events. It has seen a surge in violent crime in recent years, and police frequently have been accused of excessive use of force.

Word of the arrests came as police in Rio de Janeiro searched for a third suspect in the rape of an American student who was violated as her French boyfriend looked on during a horrific six-hour abduction aboard a minibus.

Brazil is also hosting the 2016 Summer Olympics and will welcome Pope Francis in July for World Youth Day.