TOKYO - NTT Docomo Inc. said Thursday its customers were experiencing mobile service disruptions across Japan, but it had found no signs that the problems were caused by a cyberattack.
The major telecommunications carrier said voice calls, data communications and text messaging on its standalone 5G service, known as 5G SA, have been unstable since around 11:18 a.m.
Other 5G and 4G services, as well as mobile networks offered by other businesses using NTT Docomo's network, are unaffected, it said. Emergency calls are also unaffected.
The carrier said it is investigating the cause.
Affected customers may be able to restore service by switching to 4G in their network settings, then restarting their phones or toggling airplane mode on and off, the company said.
Separately, NTT Docomo said it had suspended its online shop and "My docomo" customer portal after finding that an outside party had likely gained unauthorized access to its servers.
The carrier said the breach had resulted in the leak of personal information linked to up to 300,000 customer accounts, including names and phone numbers.
The suspension began around 1:05 a.m., leaving customers unable to use the services to sign up for mobile plans, check bills or make contract changes.
