The United Arab Emirates says a military helicopter crash has killed the pilot and co-pilot onboard.

The UAE military said in a statement Sunday the crash happened "during a routine flight over international waters." The statement did not elaborate, nor did it offer any details on the type of helicopter involved.

The UAE, one of the best-equipped militaries in the region, is part of a Saudi-led coalition now battling Shiite rebels known as Houthis and their allies in Yemen. It is also part of the U.S.-led coalition fighting the Islamic State group in Syria and Iraq.

In May, the UAE said another military air crash over water killed two on board during a training exercise.