KDDI said Monday that its au mobile phone services have been restored after calls and internet connections were disrupted across Japan for a few hours earlier in the day.
The disruption began at 7:18 a.m. across 31 western prefectures including Osaka, Kyoto and Fukuoka before spreading nationwide, said KDDI, one of the three major carriers in Japan. Services had been restored by 10:11 a.m., it said.
The cause of the outage remains under investigation. The trouble affected emergency calls as well as services offered under the company's budget brands. Some mobile service operators that rent KDDI's networks experienced a similar problem, the company said.
"We apologize for causing tremendous trouble for our customers," the company said in a statement before the resumption of the services.
KDDI also had a system glitch in July last year, which resulted in service disruptions for about 61 hours.
Top government spokesman Hirokazu Matsuno told a news conference, "It is extremely regrettable, as (KDDI's) infrastructure is important for people's daily lives and economic activities."