U.S. forces in Japan now require all of their personnel to test for the coronavirus within 24 hours after their arrival in the country, the Foreign Ministry said Friday, after a cluster infection recently broke out at a U.S. base in Okinawa.

The policy change came after the forces were criticized by Japan for exempting their personnel from testing for the virus before departing from the United States, with Foreign Minister Yoshimasa Hayashi calling for the implementation of stricter measures.

Since a group infection was reported at the U.S. Marine Corps' Camp Hansen in Okinawa Prefecture earlier in December, the forces have already required their personnel coming to Japan to undergo the testing 72 hours ahead of departure.

The forces had said the exemption from PCR tests began in September for vaccinated personnel coming to their facilities in Japan by military aircraft.

More than 250 people were known to have been infected with the virus at the base in the southern island prefecture, which hosts the bulk of the U.S. military facilities in Japan.

Japan toughened border controls in late November in an attempt to keep the Omicron variant at bay, with new measures including banning the entry of nonresident foreign nationals.