The top US commander in the Middle East has warned troops that cellphone videos shared online can help Iran target American bases, and sources tell Reuters some deployed personnel could soon be ordered to surrender their phones.

Any crackdown on mobile communications would add a new dimension to the conflict for the thousands of US troops in the region, many of whom still rely on phones to periodically message loved ones and assure them they are well.

US Central Command chief Admiral Brad Cooper, in a previously unreported letter, said Iran was benefiting from being able to see the success or failure of its strikes in near real-time by searching news reports or online posts by journalists referencing “reactions, photos, and footage from the cellphones of our troops”.

“The direct, unavoidable cost of this open-source intelligence could be measured in the lives of American service members and civilian residents in targeted Gulf countries,” Cooper wrote in his July 28 letter, a copy of which has been obtained by Reuters.

He calls on troops to “redouble our focus on operational security,” without prescribing specific steps in the memo.

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