Portugal's education minister was robbed at knifepoint on Saturday at the Olympic lake where rowing events are taking place, but escaped unharmed, authorities said.
Education Minister Tiago Brandao Rodrigues and an aide were walking near the event area when they were assaulted.
The assailant was quickly located by police at the lake, a few blocks away from Ipanema beach, and arrested. Rodrigues' belongings were returned to him.
It was the latest incident in a series of robberies that have hit visitors since the Olympics opened on Friday. Rio has dramatically lowered its crime levels in recent years, but there has been a spike in murders and assaults in recent months.
Authorities said that 85,000 soldiers and police patrolling streets for the Games - double the number of security officials in place during the London Games in 2012 - would keep Rio safe.