Paraguayan judge Clara Ruiz Díaz has ruled that former Brazil and Barcelona star Ronaldinho will remain behind bars, along with his brother Roberto, after entering the country with falsified documents.

The brothers were arrested on Friday night in the Resort Yacht & Golf Club Paraguayo after Paraguayan passports were found bearing their names.

The 39-year-old former Ballon d'Or, who is currently without a Brazilian passport over unpaid environmental fines, had traveled to Asunción to partake in several publicity events.

Ronaldinho's and Roberto's lawyer, Adolfo Marín, had asked for house arrest for his two clients, but the judge ruled against the request due to the failure to provide any documentation proving the brothers would not attempt to flee Paraguay before the investigation has concluded.

"They did not bring a single document that suggests that the court can avoid the danger of escape," said Ruiz Díaz.

Marín defended his clients' actions by pointing to the former Brazil international's ignorance of the law: "He didn't know he was committing a crime because he didn't know they'd given him false documents, he's stupid."

The brothers said the documents were offered as a gift by a Brazilian businessman, Wilmondes Sousa Liria, who has already been jailed. The lawyer added, "it was a gifted the brothers didn't give much attention."

Ronaldinho, a two-time world player of the year, last played professionally in 2015 after an illustrious career which included a 2002 World Cup win and spells at European giants Paris Saint-Germain, Barcelona and AC Milan.