Madrid, Spain's World Cup-winning captain and goalkeeper Iker Casillas has announced his retirement from football at the age of 39.

Casillas, a Real Madrid legend, suffered a heart attack during a training session last year and has not played any competitive football since April, 2019.

He recovered to rejoin the ranks at Porto and was named in their squad for the 2019-20 campaign.

Casillas, who led Spain to their first World Cup in 2010 and helped his country win the 2008 and 2012 European championships, had a low-key farewell from the club he joined in 2015 after spending 25 years at Real Madrid.

"The most important thing is the path you travel and the people who accompany you, not the destination that it takes you," Casillas wrote on his Twitter account in Spanish.

"I think I can say, without hesitation, that this has been the right path and the dream destination. Thanks."

With 167 international caps, Casillas has the second-most appearances for the Spanish national team, making him the joint tenth-most capped footballer of all time.

Casillas burst onto the scene as a teenager at Real Madrid and went on to make 725 appearances for the Spanish giants -- helping them win five LaLiga titles and three Champions League crowns.

Casillas said in February that he is keen on running for election as President of the Spanish Football Federation (RFEF).