Sheikh Abdullah bin Ali al-Thani appeared in a video recording on Sunday, saying that he was being held in Abu Dhabi against his will, presstv.com reported.
"I am now in Abu Dhabi as a guest of Sheikh Mohammed, but actually not in the position of a guest but rather as a detainee," Abdullah said, apparently referring to Abu Dhabi Crown Prince Sheikh Mohammed bin Zayed al-Nahayan.
"I just want to inform you that if anything happens to me, don't blame Qatar," he added.
After a diplomatic crisis erupted between Doha and a Saudi-led quartet of Arab countries, Abdullah emerged as a potential opposition figure and sided with the anti-Qatar alliance in several Saudi and UAE television programs.
Saudi Arabia, the UAE, Bahrain and Egypt severed diplomatic ties with Doha in June 2017, accusing the kingdom of sponsoring terrorism and destabilizing the region. Qatar has rejected the claims while maintaining that it is paying the price for its independent foreign policy.
The UAE Foreign Ministry on Sunday denied the claim that Abdullah was being held against his will, blaming Qatar.
The ministry said he had come to Abu Dhabi at his own request as a guest after the Doha government placed restrictions on him.
Abdullah "is free to move about and has expressed his desire to leave the state, all procedures were facilitated for him without any obstruction," the UAE state news agency WAM, quoted the official as saying. No details were, however, given about his destination.
Sources told Middle East Eye back in October that Abdullah was leading an initiative to declare the formation of a Qatari government-in-exile to push for regime change in the Persian Gulf emirate.
Qatar’s Foreign Ministry said that the lack of contacts with the UAE made it
difficult to be certain what had happened with Abdullah, but that it was monitoring the situation.
"In principle, the state of Qatar supports maintaining the legal rights of any individual and his family has the right to pursue all legal means to protect his rights," the statement said.
The Qatari foreign minister had said that Riyadh is pursuing ‘regime change’ in Doha, stressing that a siege laid by Saudi Arabia and its allies on the Persian Gulf nation is meant to ‘bully’ the nation.