The U.S. military on Thursday ordered personnel stationed in Japan to wear masks when going off base to curb the spread of COVID-19 infections.

American forces have come under fire after a recent spike in coronavirus cases in areas where they are based in large numbers, including Okinawa and Iwakuni, both in southern Japan.

Okinawa Gov. Denny Tamaki sent a request to Japan’s national government on Thursday asking for permission for the prefecture to strengthen its anti-COVID measures.

At least 980 people, a daily record for Okinawa, tested positive for COVID-19 on Thursday. In December, there were zero new cases on some days.

“If we all work together, we hope cases will come down,” Tamaki told reporters.

Japan has never had a lockdown, but measures have periodically been taken to restrict people’s activities, such as requiring stores and restaurants to close early or serve fewer people.

Tamaki has blamed U.S. soldiers for what he called “the alarming rise” of cases on Okinawa, which has been hit harder than the rest of Japan. He promised financial aid for businesses that abide by the restrictions.

Other prefectures with U.S. bases, such as Yamaguchi, where Iwakuni base is located, are expected to follow suit. Cases are gradually rising throughout Japan, including in Tokyo, which reported 390 new cases Wednesday. Tokyo Gov. Yuriko Koike has so far been reluctant to order restrictive measures.

Japan beefed up border controls late last year, preventing travel from abroad except for returning residents and citizens. American soldiers are basically free to enter and move about Japan under a bilateral security agreement. The U.S. is Japan’s most important ally.

COVID-19 cases among U.S. Forces in Japan now total 1,784, about a third of them on Okinawa, according to USFJ. Iwakuni has reported a total of 529 cases. Military forces coming to Japan are required to present three negative COVID-19 tests, including one before departure.

“The mitigation measures we have instituted throughout USFJ are intended to protect our force’s readiness, the well-being of our families, and the health of Japan’s citizens. We recognize we all have a part to play in keeping our communities safe,” U.S. Forces in Japan said in a statement.

This week, Japan has reported more than 2,000 cases daily. About 80% of the population has had two vaccine shots, but boosters are just getting started. Japan has so far had 18,300 COVID-related deaths. Worries are growing about the omicron variant, as some people died at home when the medical system couldn’t handle the sudden surge in cases.

Yuri Kageyama is on Twitter https://twitter.com/yurikageyama