King Juan Carlos Abdication
People take part in an anti-monarchist demonstration at Madrid's landmark Puerta del Sol Square, following the announcement of the abdication of Spain's King Juan CarlosReuters

The abdication by King Juan Carlos of Spain has sparked calls for a referendum on the country's monarchy as tens of thousands of Spaniards took to the streets across the cities demanding voting.

Madrid, Barcelona and several other cities witnessed demonstrations after the 76-year-old king announced he would be stepping down paving the way for his son Crown Prince Felipe.

Spaniards Call for Referendum on MonarchyIBTimes UK

Authorities estimate at least 20,000 people stormed the landmark Puerta del Sol square in the Spanish capital while thousands of others descended on Catalunya square in Barcelona calling for the referendum.

Several online petitions have also been filed urging the Spanish government to use the opportunity to hold the referendum.

"I think it is very good [the King's abdication]. He should have done it a long time ago. The abdication will return to the people their sovereignty," activist Alfonso Vaquez told the Associated Press.

Spain's far-left parties, which have performed better than expected in the recently-held European elections, have also called for a vote.

Juan Carlos, who was once a popular monarch as he oversaw the transition from dictatorship to democracy, decided to abdicate after 39 years on the throne. He lost much of his popularity in recent years over various scandals involving him and his family members.

The Spanish cabinet is set to meet to discuss further steps as the country presently does not have a law on abdication and succession.

The ministers are set to discuss when and how the handover of the throne to Felipe would take place. The two main parties, unlike those on the far-left, remain loyal to the royal family.