Oman said it uncovered a UAE spy network in the Gulf Arab state that targeted its government and military, the state news agency of the U.S. ally reported on Sunday.
Neighboring United Arab Emirates, a regional energy, financial and tourism hub that typically has had friendly relations with Oman, denied having links to any such network.
A regional security analyst found the allegations puzzling but suggested one possible motivation for such a network was that the UAE wanted to know more about Oman's links with Iran.
"This is all very murky," Theodore Karasik, director of research and development and research at the Dubai-based Institute for Near East and Gulf Military Analysis, said.
"One possibility is that the UAE wants to know more about Iran-Oman relations because of Tehran and Muscat's long ties in security and military cooperation."
Oman's state news agency reported that its "security services uncovered a spying network belonging to the state security apparatus of the United Arab Emirates, targeting ... Oman and the way its government and military work".
It gave few details but an Omani government official, speaking on condition of anonymity due to the sensitivity of the matter, said a number of Omani nationals had been arrested, including some of whom worked for the government.
The Omani official said the arrests dated back about two months, but gave no other details. Oman's news agency ONA said the suspects would be sent to court.
The UAE foreign ministry, in a statement carried by the state news agency WAM, said: "The UAE expresses its full willingness to cooperate with ... Oman in any investigations that it carries out in full transparency to uncover (those) who try to mar the relations between the two countries."
Oman maintains good relations with Iran and was instrumental in helping to negotiate the release of one of three U.S. hikers accused by Tehran of straying from Iraq into Iranian territory.
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