Spanish media have published images of him in the Gulf state.
Knowledge of his whereabouts will intensify pressure on Spanish authorities to pursue investigations into alleged criminal behaviour that includes money-laundering and bribery relating to a Saudi construction contract.
Catalan President Quim Torra said that allowing Juan Carlos to flee “casts doubt on the commitment of the government to fight corruption,” while the Communist Party of Spain said the crisis strengthens the case for a renewed Spanish republic.
“Democracy to Spain was brought by the Spanish people that maintained the anti-Franco resistance,” it said, “not a family who inherited the leadership of the state by decision of a dictator.
“[It] will not be complete until our people can elect all the representative institutions, including the head of state,” the party warned, adding that the command of the armed forces by an unelected head of state was doubly dangerous since there was no “constitutional mechanism by which the head of the armed forces can be held accountable.”
The ex-monarch, who ascended the throne on the death of fascist dictator Francisco Franco in 1975, was forced to abdicate in 2014 following an embezzlement scandal involving his daughter and the exposure of an elephant-hunting trip he had taken to Botswana in 2012, when Spain was implementing harsh austerity measures that had provoked an evictions crisis. The trip, which also forced him to resign as honorary president of the World Wildlife Fund-Spain, was paid for by an adviser to the Saudi monarchy linked in the Panama papers to offshore companies set up for tax-evasion purposes.