Barcelona star Lionel Messi on Tuesday said he was unconcerned about accusations of tax avoidance on income generated from the sale of his image rights and was confident his lawyers will solve the case.

Last month the 25-year-old and his father Jorge Horacio were ordered by a Spanish court to appear for questioning in September as part of an investigation into alleged tax fraud.

"I'm not worried, I'm always on the sidelines of all of that, just like my dad. We have our lawyers and our advisors who handle these things. We trust in them and they will solve the issue," he said.

"I don't understand anything about all of that, this is why we have people who handle these issues," he added at a news conference at the club's training ground.

Spanish financial crimes prosecutors filed papers with a court on June 12 accusing Messi and his father of defrauding the tax office of over four million euros ($5 million, £3.4 million) in income related to the use of his image from 2006-2009.

Messi and his father aimed to deceive the state by ceding the player's image rights to companies based in tax havens such as Belize and Uruguay so they would pay no tax in Spain, according to the prosecutor's complaint filed at a court in Gava, a Mediterranean coastal town near Barcelona.

The prosecutor's complaint also alleged the four-time World Player of the Year and his father drew up deals related to his image rights in Britain and Switzerland, ensuring that the income went straight to the tax havens without any tax being paid.

The accusations of tax fraud are a huge blow to the prestige of Messi, who has long been seen as a more humble figure than most top-class footballers -- in particular his fierce Real Madrid rival Cristiano Ronaldo.

Messi's lawyers office, Juarez Veciana, have said the player "scrupulously complies with Spanish legislation" and will "pay any amount that he is eventually found to owe".