Hundreds of protesters demonstrated in Madrid on Sunday against tarnished former king Juan Carlos I, whose visit to Spain after almost two years of self-imposed exile in the UAE has sparked criticism.

Holding signs reading "Justice" and "The Bourbon in prison", the demonstrators gathered near the Spanish capital's royal palace. A government spokesman put their number at 300.

Juan Carlos this week returned to Spain for the first time since August 2020 to attend a regatta, after investigations into alleged corruption and money laundering were shelved in March.

The 84-year-old was admired for his role in Spain's democratic transition following the death of dictator Francisco Franco in 1975, but revelations about the opaque origins of his fortune have tarnished his reputation among many Spaniards.

The former monarch is due to visit his son King Felipe VI in Madrid on Monday before returning to the Emirati capital Abu Dhabi, his new permanent residence.

Socialist Prime Minister Pedro Sanchez's government still expects "explanations" from Juan Carlos, who abdicated in favour of Felipe in 2014. Media reports say the government opposes his staying at the Zarzuela Palace, Felipe's official residence.

But in the northwestern port of Sanxenxo, where Juan Carlos competed in the regatta this weekend, dozens of onlookers welcomed him, shouting "Long live the king, long live Spain!".