MADRID: King Juan Carlos of Spain abdicated from his position as head of state Monday.
The king's decision was announced to the nation by Prime Minister Mariano Rajoy, who called a press conference at a short notice to make the "institutional declaration", Xinhua reported.
"His majesty the King Juan Carlos has just told me he will renounce the throne, and to open the succession process," Rajoy said at the press conference.
The Spanish royal household posted a photo on Twitter showing King Juan Carlos signing the paper.
"I want to say that I have found the king convinced that this is the best moment for this change of the head of state and the transfer of the crown to the Prince of Asturias to happen," said Rajoy.
"I will call an emergency cabinet meeting Tuesday with the aim of completing the constitutional previsions," he added.
The 76-year-old monarch was named the king of Spain Nov 22, 1975, two days after the death of General Franco, who had nominated him as his successor.
The king embarked on a process to bring democracy to Spain and was a key figure in the failed military coup of Feb 23, 1981, when he made a television broadcast asking for the unanimous support to the democratic government.
However, the king's popularity has declined in recent years.
Juan Carlos was heavily criticised for extravagant vacations while his country was suffering an economic crisis.
He also suffered a series of health issues such as a benign tumour which he had removed and a broken hip, which he suffered in April 2012 while elephant hunting in Botswana.
The monarch later took the unprecedented step of apologising to the nation, although that did little to save his popularity from falling to the lowest levels of his reign.
Juan Carlos will be succeeded to the throne by his son, 46-year-old Felipe Juan Pablo Alfonso de Todos los Santos de Borbon, the Prince of Asturias, who will be called King Felipe VI.