Portugal's Cristiano Ronaldo celebrates scoring their first goal while playing against Latvia in 2018 World Cup Qualifying European Zone on June 9, 2017. [Photo/Agencies]

The prosecutor's office said the Real Madrid forward had knowingly used a business structure created in 2010 to hide his image-rights income in Spain between 2011 and 2014.

This involved a "voluntary" failure to comply with his tax obligations in Spain, the statement from the office's economic-crimes section said.

The four counts of tax fraud were based on a report from Spain's tax agency, it said in a statement.

Ronaldo denied the accusations through his representatives late on Tuesday.

"There is no tax evasion scheme, there has never been any hiding nor any intention to hide anything," Gestifute, the agency representing the player, said in a statement.

Gestifute said it would publish documents to show the Portuguese superstar had not created such a structure and had instead used firms he had owned since his time at Manchester United that both British and Spanish tax authorities were aware of.

The agency also said the case could relate to different interpretations between the British and Spanish tax systems over where to declare some revenues but would, in any case, not constitute fraud.

Ronaldo, who led Madrid to its 12th European Cup earlier this month, is the latest in a long line of soccer stars in Spain - among them Barcelona's Lionel Messi and Neymar - to be caught up in cases over tax or transfers.

Between 2005 and 2010, foreign players in Spain were protected under the so-called "Beckham law", allowing them to curb taxes. But as the financial crisis bit deeper, that exemption was lifted.

The prosecutor's office alleges Ronaldo defrauded tax authorities of 1.4 million euros in 2011, 1.7 million euros in 2012, 3.2 million euros in 2013 and 8.5 million euros in 2014.