The Japanese government on Monday ordered messaging app provider Line Corp. to take measures to properly protect customers' information after such data were found accessible by a Chinese affiliate without user consent.

The administrative guidance, which also requires a report from Line by late May, was issued as the Internal Affairs and Communications Ministry judged the app operator failed to provide a sufficient surveillance system to protect the "secrets of communications" as required by law.

Line said in a statement it takes the government's order seriously and vowed to "regain users' trust by implementing the appropriate reforms."

The move came after Line, used by over 86 million of Japan's some 126 million people, said last month that users' personal information had been accessible by technicians of its Chinese affiliate.

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Photos and video footage posted by its users on the online platform were also stored at a server in South Korea.

The communications ministry also said four technicians at the company's Chinese affiliate accessed the app operator's database 132 times, more than what had been declared earlier by Line.

On Friday, the government's Personal Information Protection Commission issued a separate administrative guidance and asked Line to report improvement measures within a month to provide a sufficient surveillance system, although there was no clear violation of the personal information protection law.

In its data protection guideline, Line has said that customers' personal information can be sent overseas but did not specify the name of any foreign country despite being required to do so under a legal change last year.

The app operator has said that four technicians in the Chinese affiliate accessed its database at least 32 times. They were able to see users' names, phone numbers and email addresses, along with messages reported by users as inappropriate from around the summer of 2018.

To better protect customers' information, Line has said data that are stored in South Korea will be transferred to databases in Japan.

After the issue came to light in mid-March, Japanese government ministries and other public organizations have temporarily suspended use of the app as a communications tool with the public amid security concerns.

Some security experts have expressed concern that personal information of Japanese users may be handed over to Chinese authorities based on the country's national intelligence law.

The Line app has also been popular as a major social communications tool in Taiwan, Thailand and Indonesia since the service was launched in June 2011.