Tokyo on Thursday reported 641 new COVID-19 cases, the highest daily tally since Sept. 18, as Japan entered its sixth wave of infections with a sharp rebound in cases amid the spread of the highly transmissible Omicron variant.

The figure came a day after the one-day tally in the Japanese capital hit 390 and at a time when there are concerns over the spread of the new variant at U.S. military bases in Okinawa Prefecture in the country's southwest.

The daily figure for Tokyo has more than tripled in just three days since hitting 103 on Monday, the first time the number was in the triple digits in about three months.

Nationwide, daily cases surpassed 4,000 on Thursday for the first time since Sept. 18.