The president of major Japanese mobile carrier KDDI says the company is working to fully restore its services, but did not mention the exact timing. KDDI's "au" mobile service went down early Saturday morning, making it impossible to place voice calls or access the internet.

KDDI President Takahashi Makoto told reporters on Sunday morning that recovery work had been completed around 11 a.m. in its western Japan service area and is expected to be finished by around 5:30 p.m. in its eastern Japan service area.

Takahashi said his company will decide later when services will be fully available.

The president said he recognizes this is a serious incident under the country's relevant law and will take appropriate measures after promptly restoring services.

KDDI estimates that the disruption has inconvenienced up to 39.15 million users. The outage has also affected users of UQ mobile and povo, which use KDDI's network. Logistics and many aspects of people's lives have also been disrupted.

Communications minister Kaneko Yasushi told reporters on Sunday that he is taking the incident seriously.

He said the telecommunication glitch made it difficult to respond to some emergency calls, which is a critical function that protects people's lives and assets.

The minister said this is especially serious at a time when the risks of the coronavirus and heat stroke are increasing and a tropical storm is approaching Japan's archipelago.

He said this could constitute a serious incident under the Telecommunications Business Act. He said his ministry will take necessary measures after receiving an official report from KDDI.