Brazil and Barcelona great Ronaldinho maintains his innocence after being arrested for entering Paraguay with a fake passport, adamant the illegality of the document was a complete surprise.

Ronaldinho and Roberto Assis, the former footballer's brother and agent, were arrested on March 6 shortly after arriving in Asuncion to promote a book and the launch of an online casino.

Local authorities shared an image of what appeared to be a Paraguayan ID card bearing Ronaldinho's name and photo, with the former Ballon d'Or winner and his sibling taken into custody despite prosecutors proposing a different sanction, arguing the pair had been tricked.

The pair protested their innocence but spent 32 days in prison before being released and placed under house arrest in a hotel on April 8.

While the investigation is ongoing, Ronaldinho gave his first interview since the arrest, insisting he had no idea the ID card was fake.

"We were totally surprised to learn that the documents were not legal," Ronaldinho told Paraguayan TV station ABC Color.

"Since then our intention has been to cooperate with justice to clarify the fact, as we did from the beginning. From that moment until today, we have explained everything and facilitated everything that justice asked of us.

"It was a hard blow, I never imagined I would go through a situation like this. All my life I have sought to reach the highest professional level and bring joy to people with my football.

"We hope that they can use and confirm everything we provide as soon as our possible in the case and that we can leave this situation.

"Everything we do is under contracts that are managed by my brother, who is my manager. In this case, we came to participate in the launch of an online casino, as specified in the contract, and for the launch of the book 'Craque da Vida' that was organised with the company in Brazil that has the rights to exploit the book in Paraguay."

Ex-Barca, Paris Saint-Germain and Milan forward Ronaldinho won 97 caps for Brazil between 1999 and 2013. 

He scored 33 times and was a key part of the 2002 World Cup-winning squad.