'Casillas is ok, stable and the heart problem has been resolved.'
Spain's World Cup winning captain Iker Casillas, 37, suffered a heart attack while training with his team Porto on Wednesday and was taken to hospital, the Portuguese club said in a statement, adding that the goalkeeper's life was not in danger.
"Iker Casillas suffered an acute heart attack during this Wednesday's training session," Porto said in a statement on their official website.
"The session was quickly halted so medical assistance could be provided to the Porto goalkeeper, who is currently in the CUF Porto Hospital. Casillas is OK, stable, and the heart problem has been resolved."
The club's official Twitter account added: "Always together. Stay strong, Iker."
Casillas played 167 times for Spain, famously captaining his country to their first and only World Cup win in 2010 as well as the 2008 and 2012 European Championships.
His exploits for the national team earned him the nickname 'Saint Iker' and made him one of the best known personalities in Spain. He is married to the television journalist Sara Carbonero, with whom he has two children.
Born in Mostoles, Madrid, Casillas came through Real Madrid's academy and spent the majority of his career there until joining Porto in July 2015.
He is Real's second all-time appearance maker, playing 725 matches between 1999 and 2015, winning five La Liga titles and three Champions League crowns with the club. His former team mate Raul made 741 appearances for Real.
Madrid wished their former captain a full recovery.
"Real Madrid would like to offer all our support to our beloved captain Iker Casillas. Throughout his professional career, he always overcame the hardest challenges in order to bring glory to our club," Real said in a statement.
"He has taught us to never give up and has shown us numerous times that the best way to win is to remain as strong as possible when times are tough. Real Madrid and all our fans wish him a speedy recovery and send him all our support."
A tweet on the Spain team's official account said: "All the family at the national team and the Spanish football federation are with you Iker Casillas. Get well soon."
