Spain's former king Juan Carlos (left) hands over a letter of abdication to Spain's Prime Minister Mariano Rajoy at the Zarzuela Palace in Madrid on Monday. Spanish former king Juan Carlos announced his abdication in favor of his son Prince Felipe, ending a 39-year reign. Photo: AFP/CASA REAL

Spain's former king Juan Carlos, who is facing investigation at home and abroad for corruption, announced Monday that he will go into exile.

The 82-year-old revealed he would leave the country in a letter to his son, the current King Felipe VI who accepted his decision and thanked him, the royal palace said in a statement.

"Guided by the conviction to best serve the people of Spain, its institutions, and you as king, I inform you of my decision at this time to go into exile outside Spain," Juan Carlos wrote.

"It's a decision I take with deep anguish, but great peace of mind," he added. He did not say where he would go.

Probes are under way in Switzerland and Spain where media regularly publish details of the murky management of funds allegedly paid to the former head of state by Saudi Arabia.

Spain's Supreme Court announced in June an investigation to determine the legal responsibility of the ex-monarch - but because of the immunity he holds only for acts committed after his abdication.

The suspicions focus on $100 million alleged to have been paid secretly into a Swiss bank account in 2008.

After a series of media revelations, Socialist Prime Minister Pedro Sanchez spoke out in July saying, "the entire Spanish population are receiving disturbing information which is troubling for us all, including me."

The former king's lawyer Javier Sanchez-Junco, issued a statement on Monday saying that his client was not trying to escape justice by going into exile and would remain available to prosecutors.

Juan Carlos ascended the throne in 1975 on the death of the fascist dictator Francisco Franco and ruled for 38 years before abdicating in favor of his son Felipe VI in June 2014.

AFP