Ronaldo was suffering with ankle problem since last month and scans proved he aggravated the injury while on international duty with Portugal at the weekend.

"A clinical examination and a scan showed the player had suffered a recurrence of the injury to his right ankle," Real said in a statement on their website.

"Estimated time out of action three to four weeks depending on clinical developments."

Ronaldo now looks certain to miss the Champions League with AC Milan next week, in addition to league games with Valladolid, Sporting and Getafe.