The State Department has warned U.S. citizens traveling in China that they face “scrutiny and harassment” in the country following a string of high-profile detentions by Beijing’s authorities. The warning urges U.S. citizens traveling in China to exercise increased caution due to “arbitrary enforcement of local laws,” with dual U.S.-Chinese nationals believed to be at particular risk from exit bans that prevent them from leaving. Both Canada and the U.S. have seen diplomatic ties with China strained after Canadian police arrested Huawei’s chief financial officer, Meng Wanzhou, in Vancouver at Washington’s request. Canada says 13 Canadians—including Michael Kovrig, a former diplomat, and businessman Michael Spavor—have been detained since Meng’s arrest in December. The State Department says that, because dual-citizenship is not recognized under Chinese law, “U.S.-Chinese citizens and U.S. citizens of Chinese heritage may be subject to additional scrutiny and harassment.” Citizens are urged to enter China on U.S. passports with a valid Chinese visa, and contact the U.S. Embassy or the nearest consulate immediately in the event of being arrested. China hit back at the new advice, with a foreign ministry spokesman saying Friday that 2.3 million Americans visited China in 2018, and that some Chinese citizens have encountered difficulties entering the U.S.