Brazil arrests 10 over alleged Olympic terror plot

Brazil's federal police have arrested 10 people for allegedly planning terrorist attacks during next month's Olympic Games in Rio de Janeiro.

Justice Minister Alexandre Moraes described the group as "absolute amateurs", adding that their detention was a preventative measure.

Officials said the suspects had tried to make contact with Islamic State, but were not members of the organisation, Xinhua reported.

The arrested people were all Brazilian citizens and were detained in 10 different states. They had been in contact via mobile messaging services like WhatsApp and Telegram, police said.

Thursday's developments came a week after 84 people were killed, including scores of children, when a truck ploughed through a crowd celebrating Bastille Day in the southern French city of Nice.

Brazil's institutional security minister, Sergio Etchegoyen, said after the Nice attack that security would be raised to "another level" for the August 5-21 Games.

Brazil's federal police are understood to be monitoring 100 people for possible links to terrorist groups. Meanwhile intelligence agencies are stepping up security and tightening checks in the tri-border region with Argentina and Paraguay.

"Today was the first operation against a supposed terrorist cell in Brazil," Moraes said. "Brazil was not part of the coalition against IS, but because of the upcoming Olympics and because it will receive many foreigners, Brazil becomes part of the target."

Agents from more than 100 countries and regions are working in tandem with Brazil's federal police and armed forces during the Games period, according to the government.

Brazil is also reportedly planning a special security arrangement at the opening ceremony for French President Francois Hollande.

South America's largest country will deploy 88,000 soldiers and police during the Olympics, more than double the number at the London 2012 Games.