The alert by the State Department comes two days after a general strike and widespread demonstrations shook the city, and as Chinese officials have warned about the continuing unrest.

“Since June 2019, several large scale and smaller political demonstrations have taken place in various areas of Hong Kong,” the advisory warned. “Most have been peaceful, but some have turned confrontational or resulted in violent clashes. The protests and confrontations have spilled over into neighborhoods other than those where the police have permitted marches or rallies. These demonstrations, which can take place with little or no notice, are likely to continue.”

Several other countries, including Australia, Britain, Ireland, Japan, and Singapore, have issued similar travel warnings.