After the government expressed great concern over a surge of new infections and sought for restrictions on the movement of US personnel, US military bases in Japan implemented stricter COVID-19 measures on Thursday.

Japan is experiencing its sixth wave of coronavirus infections, with cases in some areas reaching new highs in recent months. One official blamed US military forces for the spread of the Omicron variant.

US forces in Japan said that due to a spike in COVID-19 cases at US bases and throughout Japan, it was implementing stricter mitigation measures, including mandating US military personnel to wear masks off base and stricter testing.

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"The mitigation measures we've put in place are designed to protect our force's readiness, our families' well-being, and the health of Japan's citizens," the force said in a statement. "We recognise that we all have a role to play in ensuring the safety of our communities."

Over 100,000 US service members, dependents, and contractors are stationed in Japan.

Foreign Minister Yoshimasa Hayashi has previously requested that US Secretary of State Antony Blinken limit US service members to their bases, according to Chief Cabinet Secretary Hirokazu Matsuno, who said that Japan was "gravely concerned" about COVID cases at US bases.

The southern prefecture of Okinawa, which is home to 70% of Japan's US military bases, is at the epicentre of Japan's current spike of cases and it has urged the central government to impose new limitations, known as quasi-emergency measures, which would likely include limiting restaurant and bar opening hours.