Ronaldo determined to leave Spain: reports

Cristiano Ronaldo wants to leave Real Madrid and Spain after being accused of committing tax fraud

Real Madrid star Cristiano Ronaldo appears determined to quit Spain as he believes he is being singled out for unfair treatment by the tax authorities.

Press Association Sport understands the 32-year-old is "outraged" after prosecutors accused him of defrauding the authorities of 14.7 million euros ($A21.6 million).

A source claims the Portugal international "feels great indignation" with the speculation about his tax affairs and and a sense of "injustice" at the allegations - which he contests - and has made a decision to leave Spain.

Earlier this week Ronaldo's agency Gestifute released a statement which read: "There is no tax evasion scheme... There has never been any hiding nor any intention to hide anything."

On Thursday Ronaldo, who signed a new five-year contract in November, posted a picture of himself with his fingers to his lips on Instagram with the caption "Sometimes the best answer it's to be quiet".

Real Madrid said on Thursday they were confident the Portuguese forward had acted legally.

Ronaldo's tactics are not dissimilar to those of Barcelona's Lionel Messi who took a similar stance in threatening to quit Spain in 2014, also claiming he had been singled out for special treatment, when he was accused of concealing 4.1 million euros ($A6.1 million) from the authorities.

The Argentina forward was found guilty and subsequently lost an appeal against a 21-month prison sentence (under Spanish law sentences under two years are usually suspended) and a fine of 2.1 million euros ($A3.1 million).

As one of the most marketable players in the world, Ronaldo's potential availability would generate much interest, but only the very richest clubs in the world would be able to afford him.

In November, he agreed to extend his Real contract until 2021 with a buyout clause understood to be 1billion euros ($A1.47 billion).

In May, Forbes calculated his pre-tax salary as being close to Stg45 million ($A75.4 million) a year.

The EURO 2016 winner has helped Real secure the Champions League three times, scoring twice in last month's final as they became the first club to retain the title, and he became only the second player to score in three finals. He is the competition's record goalscorer with 105.

He has also won two La Liga titles with the club he joined from Manchester United for a then world record fee of 96 million euros ($A140.9 million) in 2009.

Ronaldo is currently at the Confederations Cup in Russia with the Portuguese national team.