Madrid: Whistleblowing website Football Leaks, which specialises in publishing secret documents from the football world, has revealed that when Argentine forward Sergio Aguero was transferred to Manchester City in 2011, Atletico Madrid did not include any clause preventing the striker's sale to Real Madrid, Spanish newspaper Marca reported on Wednesday.

Sergio Aguero. Pic/ PTI

Real Madrid did include an 'anti-Barcelona' clause in the transfer contracts of Angel Di Maria and Mesut Ozil before moving to Manchester United and Arsenal, reports Efe.

Atletico agreed to sell Aguero to City in 2011 for 36 million euros ($40 million), with variables that reached a maximum of 2 million ($2.2 million) until the 2015-16 season.

City also agreed to pay the Rojiblancos one million euros ($1.1 million) every time they won the English Premier League (EPL) title with Aguero and one million more if they made it to the Champions League semi-finals.