Brazil's armed forces and federal intelligence body Abin have been monitoring international terrorist groups following recent attacks in Paris and Brussels, the official said on Wednesday, Xinhua news agency reported.
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Defence Minister Raul Jungmann said Brazil's intelligence agencies were working alongside counterparts in the US, Britain, France, Israel and Russia.
"Our intelligence organs have a contract with several countries. There has not been any threat on our radar," Jungmann told reporters in Rio.
"It's an area where you have to expect the unexpected, but until now we have had no alert or sign that a terrorist entity is focusing on Brazil," Jungmann said.
He added that the absence of "ethnic, religious and border conflicts" meant Brazil was less likely to be targeted by terrorists.
In addition to collaborating with several countries and regions to monitor security at the August 5-21 Games, Brazil will deploy tens of thousands of troops in Rio's streets to ensure the safety of athletes, officials, residents and an estimated 600,000 foreign visitors.
In total there will be 85,000 security personnel - including armed forces, police and security agents - patrolling the city during the Games.
The figure is more than double the number deployed at the London 2012 Olympics.