Japan's officials are monitoring a rapid spread of coronavirus infections. Okinawa confirmed 623 new cases on Wednesday... well over double the day before.

The southwestern prefecture is not the only area where tallies are rising.

Okinawa was a hotspot earlier in the pandemic. This was the first time that the prefecture's daily tally topped 600 in more than 4 months.

Officials there are considering whether to ask the central government to declare a quasi-emergency. That would allow Okinawa to introduce stricter anti-virus measures.

Tokyo also saw a spike in cases, on Wednesday, reporting 390 new infections. The capital's daily tally almost quadrupled in the span of just two days.

Across Japan, authorities confirmed more than 2,000 cases for the first time in more than three months.

The spike is partly attributed to the Omicron variant. Japan's government is currently asking anyone infected with the strain to stay in hospital.

Their close contacts are asked to isolate at designated facilities. But the government is easing the measure.

Health Minister Goto Shigeyuki said, "Local governments can change these rules if they confirm that there is a rapid spread of infection in their area, and if they expect the medical system and the work of public health officials will come under strain."

The official case counts do not include infections reported on US military bases in Japan which are seeing a surge in new cases.

182 people at the Marine Corps Air Station Iwakuni were confirmed to be infected on Wednesday.

The mayor of Iwakuni says that's likely fueling the rapid spread of Omicron in his city.

Mayor Fukuda Yoshihiko said, "We've heard that the genome of the coronavirus from the base workers and those who tested positive at restaurants in the city is the same. It's highly likely that the Omicron variant has spread from the base throughout the city."

Elsewhere, 57 people at Yokota Air Base in Tokyo, 41 at Camp Fuji in Shizuoka Prefecture, and 16 at Sasebo Navy base in Nagasaki Prefecture were confirmed to be infected.

US Marine Corps' Camp Hansen in Okinawa logged a major cluster of infections in December.

The US forces then revealed it did not require new personnel to be tested until at least five days after arriving in Japan.

At the urging of Japan, the US forces now require tests before service members leave the US and immediately after they arrive in Japan.