The Spanish royal and the arms dealer have been friends for 30 years and share a common hobby — hunting, according to the outlet.
"The relationship cooled down, but due to the loneliness of both in Abu Dhabi it revived," a source close to Juan Carlos told the newspaper.
El Assir, aged 71, is reported to make frequent visits to Juan Carlos in a private residential complex. One of the sources told the outlet that the arms dealer uses friendship with royalty as a "shield" against judicial proceedings.
The arms dealer has repeatedly failed to appear at court hearings in his case, in which he is accused by Spanish justice of evading a total of about 15 million euros (nearly $17 million) in taxes. In 2019, the authorities issued an international search and arrest warrant for El Assir, for whom the prosecution requests eight years in prison and payment of nearly 90 million euros for a fine and compensation to the Spanish Ministry of Treasury.
The private life of Juan Carlos, who abdicated in favour of his son, Felipe VI, in 2014 while keeping the title of king, is no longer linked to the Spanish monarchy, a royal spokesperson told the newspaper.
In 2020, Juan Carlos left his country for the UAE following a major corruption scandal, which moved Felipe VI to deprive his father of funds from the Royal Household.