The South Korean port city of Busan will be off-limits to all U.S. military personnel starting 6 p.m. Saturday, U.S. Forces Korea announced in a statement Friday.

“Due to the continued rise of confirmed COVID-19 cases and increased incidence rates in Busan,” the announcement states, “and out of an abundance of caution to protect the force,” all travel to or within Busan is off-limits.

COVID-19 is the respiratory disease caused by the coronavirus.

Exceptions are made for residents of Busan and for individuals on official and necessary duties, according to the statement. Also, “bubble-to-bubble” travel for Busan residents remains authorized to other USFK installations.

Busan, the second most populous city in South Korea, joins the capital, Seoul, as off-limits to U.S. military personnel on the peninsula.

Seoul on Friday imposed an order closing businesses overnight between 9 p.m. and 5 a.m., according to a news release.

“The flame of [of COVID-19] is spreading wildly in the city now,” the release states. “The city is getting into a desperately dangerous situation.”

Seoul reported 167 new coronavirus infections Friday. The city accounts for about one-quarter of the 36,000 active cases in South Korea, according to the Central Disease Control Headquarters website.