Former Brazil forward Ronaldinho Gaucho was arrested in Paraguay on Friday, hours after a judge refused to ratify a prosecutor's proposal for an alternative punishment for attempting to enter the country with an altered passport.

Gilberto Fleitas, the head of the investigations unit of the Paraguayan police, said Ronaldinho and his brother, Roberto Assis, were taken into custody despite the prosecutor's proposal on Thursday.

"The detention order has been carried out," Fleitas told Reuters.

TV pictures showed the pair being taken in a police vehicle from the Sheraton hotel in Asuncion to a police station on the outskirts of the city.

Paraguayan prosecutor Federico Delfino announced on Thursday that he would not charge Ronaldinho for possession of an altered passport because the brothers recognized they had committed a crime unwittingly.

"We are looking for an alternative way out of this that doesn't result in a formal accusation and that recognises that these people were, we can say, taken by surprise," Delfino told reporters in the Paraguayan capital.

However on Friday, judge Mirko Valinotti denied the request for an alternative punishment and a fine payable to a local charity for Ronaldinho and sent the case back to the attorney general's office, which ordered the arrest.

Ronaldinho and his brother, who also is his business manager, are expected to face a judge on Saturday who will decide whether to free the pair or keep them in custody while investigations continue.

Their unexpected arrest came just hours after the two brothers appeared set to leave the landlocked South American nation and draw a line under their tumultuous stay that began Wednesday when they were questioned by police after presenting falsified passports on arrival at the Asuncion airport.

The brothers left Guarulhos airport in Sao Paulo on Wednesday with Brazilian passports and were given Paraguayan passports as soon as they got off the plane in the Paraguayan capital.

The men said the passports were a gift, and an investigation indicated the numbers on the passports corresponded to other people, according to the prosecutor.

Ronaldinho and his brother could not explain why they showed Paraguayan passports when they had travelled recently on their Brazilian passports to China, Europe and the United States.

Brazilians do not need a passport to travel between Brazil and Paraguay, both of which are members of the Mercosur bloc.

Ronaldinho, a soccer legend in Brazil who played for Barcelona, Flamengo and Paris Saint-Germain, was invited to Paraguay by a local casino owner to take part in a soccer clinic for children and a book launch.

The 39-year-old was named FIFA World Player of the Year in 2004 and 2005 and won the World Cup with Brazil in 2002 and the Champions League with Barcelona in 2006.