Worried about surviving a mugging during the Rio Olympics? Have a banknote ready in your pocket to keep your attacker happy.

That's the advice French visitors heading for the Games are getting from their government to minimize the risk of being hurt in the notoriously dangerous Brazilian city.

France's security advisory recommends that tourists walk Rio streets with no jewelry or valuables, and carry a spare 20-real or 50-real bill ($6 or $15) ready to give to a mugger.

"The idea is that it's best not to resist an assault and always useful to have a 20 - or 50-real bill to keep the robber happy," French embassy spokesman Thibaut Lespagnol said.

As many as half a million foreign tourists are expected to descend on Rio for the first Olympic Games to be held in South America Aug 5-21, and Brazil is deploying 88,000 police and troops to protect them from terrorist threats and dissuade muggers.

Rio de Janeiro has a high incidence of crime, including pickpocketing and armed robberies that can happen at any place and at any time, a US State Department advisory said.

Credit card fraud and ATM scams are also endemic and visitors should check their accounts regularly for unexpected withdrawals, it said.

Rio's colorful hillside shanty towns, called favelas, are rife with drug trafficking and armed violence, despite a "pacification" program that placed police stations in some of them, and can be dangerous for curious visitors.

"Even pacified favelas can be unpredictable and dangerous. US visitors who visit favelas could be placing themselves at risk," the State Department advised.