The US warned its citizens in China to “exercise increased caution” due to heightened risk of arbitrary law enforcement including detention and a ban from exiting the country.

“US citizens may be detained without access to U.S. consular services or information about their alleged crime,” the State Department said, adding that U.S. citizens may face “prolonged interrogations and extended detention” for reasons related to state security.

“Security personnel may detain and/or deport U.S. citizens for sending private electronic messages critical of the Chinese government,” it added.