TOKYO (Kyodo) -- Japanese megabank MUFG Bank said Friday it has mostly resolved technical issues affecting its internet banking service after being hit by a suspected cyberattack.

The main banking unit of Mitsubishi UFJ Financial Group Inc. believes it may have been the victim of a distributed denial-of-service, or DDoS attack, in which networks are overwhelmed by data from multiple sources over a short period.

There was no leakage of customer information or damage caused by computer viruses, the company said.

According to the bank, internet services such as biometric logins started experiencing technical difficulties from 2:47 p.m. Thursday, but services were mostly restored by Friday evening.

The bank attributed the temporary disruptions, which also affected corporate services, to a large influx of unauthorized external data and issued a statement apologizing for the inconvenience.