Former Spanish king Juan Carlos has been staying at Abu Dhabi's exclusive Emirates Palace Hotel since leaving Spain aboard a private jet on Monday under a cloud of financial scandal involving Saudi Arabia, newspaper ABC said on Friday.

United Arab Emirates officials and the Emirates Palace Hotel did not immediately respond to requests for comment.

Dogged by mounting corruption allegations, Juan Carlos, 82, abruptly announced his decision to leave Spain on Monday but there has been no official confirmation of his whereabouts, setting off an international guessing game.

ABC said a private plane en route from Paris to Abu Dhabi stopped off in the northwestern Spanish city of Vigo to pick up Juan Carlos, four security guards and one other person on Monday morning.

Upon arrival at Abu Dhabi's Al Bateen airport, the ex-king and his entourage were flown by helicopter to the government-owned Hotel Emirates Palace, according to ABC, a pro-monarchy Spanish daily.

A palace spokesman said he did not know where Juan Carlos was. The former king's lawyer did not immediately reply to a request for comment. His lawyer, the royal palace and the government have all declined to say where Juan Carlos is.

Some media have speculated Juan Carlos is in a luxury resort in the Dominican Republic and others place him in Portugal, where he spent much of his youth. But officials in both countries have said they have no knowledge of him arriving.

In June, Spain's Supreme Court opened a preliminary investigation into Juan Carlos' involvement in a high-speed rail contract in Saudi Arabia, after Switzerland's La Tribune de Geneve newspaper reported he had received $100 million from the late Saudi king. Switzerland has also opened an investigation.

The former monarch is not formally under investigation and has repeatedly declined to comment on the allegations.

The lawyer said on Monday his client was at the Spanish prosecutor's disposal despite his decision to leave.

Spain and Abu Dhabi have an extradition agreement, signed by Juan Carlos himself in 2010.

 (Reuters -Reporting by Nathan Allen and Isla Binnie)