Two men aged 20 and 22 have been taken into custody and a third is being sought in connection with the incident, which saw the two foreigners held for around six hours starting shortly after midnight on Saturday, police said.
The statement said the suspects forced other passengers to get out of the van and then sexually assaulted the female tourist inside the vehicle, which was one of a fleet of vans that serve bus routes and seat about a dozen people. During the alleged assault, the tourists were driven to the poor suburban neighbourhood of Sao Goncalo, where the two suspects were apprehended, the statement said.
The victims' nationalities have not been released, but local media reports have said the woman is American. Reports said the two had been studying Portuguese in Rio for about a month and that both left the country following the incident.
The statement said one of the victims' cellphone was found in the suspects' possession. The suspects had also used a debit card belonging to one of the victims at two gas stations, the statement said.
The Globo television network broadcast surveillance camera images of two men filling up the white van and showed police images of a metal bar the suspects are thought to have used to beat and intimidate the victims.
The victims positively identified the two suspects, and a Brazilian woman has said she'd also been assaulted by the pair on March 23, the statement said.
In an interview with Globo television, commanding officer Alexandre Braga, who heads the Rio police unit specializing in crimes against tourists, said the suspects had gone on a sex crime spree.
"The characteristics of both crimes, both the Brazilian case and the one with the foreigners, lead us to believe that they (the suspects) wanted to have a 'party of evil,' in quotes," Braga said. "The principal motive appears to have been the satisfaction of their lust."
He added that the robbery and other crimes appear to have been "secondary."
Multiple calls to police seeking further detail Monday have not been returned.
The incident raises new questions about security in Rio, which has cracked down on once-endemic drug violence in preparation for hosting next year's soccer World Cup and the 2016 summer Olympic games. The city will also be playing host to World Youth Day, a Roman Catholic pilgrimage expected to draw some 2 million people in late July.
The attack also drew comparisons with the fatal December beating and gang rape of a young woman on a New Delhi bus. Six men beset a 23-year-old university student and male friend after they boarded a private bus, touching off a wave of protests across India demanding stronger protection for women.
In Brazil, more than 5,300 cases of sexual assault were reported between January and June 2012, according to the country's Health Ministry.