The U.S. State Department issued a travel advisory Thursday for Americans planning trips to China, warning U.S. citizens to "exercise increased caution" when visiting the communist nation.
"US citizens may be detained without access to. consular services or information about their alleged crime", the advisory reads.
The development comes in the wake of detention of two Canadians by Chinese authorities last month on charges of activities that "endanger China's security".
"U.S. citizens may be subjected to prolonged interrogations and extended detention for reasons related to 'state security, '" the advisory says.
The guidance warned that authorities in Beijing have used so-called "exit bans" to keep USA citizens from leaving China, sometimes holding them "for years".More news: Netflix Warns Against People Doing 'Bird Box Challenge'
The advisory noted that China can hide exit bans from US citizens until they attempt to leave China, the bans can last for unspecified durations that run into years, and those facing exit bans have been "harassed and threatened".
Michael Kovrig, a former diplomat and an adviser with the International Crisis Group (ICG) thinktank, and businessman Michael Spavor, were detained after Canadian police arrested Huawei executive Meng Wanzhou at the request of the US.
Separately, three U.S. citizens were accused of committing "economic crimes" and barred from leaving China in November. So here's what you need to know before going to China, according to the US State Department. Earlier on Thursday, China's top prosecutor said the two Canadians had "without a doubt" violated the law.
USA prosecutors have accused Meng, the Huawei CFO, of misleading banks about transactions linked to Iran, putting the banks at risk of violating sanctions.
Chinese foreign ministry spokesman Lu Kang hit back at a regular press briefing in Beijing Friday.
Beijing a year ago appeared to hit back at Washington's travel advice by issuing its own guidance to Chinese coming to the U.S., warning of the risk of mass shootings and the high cost of healthcare as well as robberies, searches and seizures by customs agents, telecommunications fraud and natural disasters.