Seoul: A total of 278 cases of unauthorized mobile payments worth 170 million won (US$122,000) have been reported by KT Corp. users as of Wednesday, raising concerns over a possible leak of customer data at the country's second-largest mobile carrier, the government said.

According to Yonhap News Agency, Second Vice Minister Ryu Je-myung of the Ministry of Science and ICT revealed the scope of damage among affected KT subscribers at a press conference at the government complex in Seoul. "The ministry has determined this breach at KT to be a serious incident, particularly given the financial losses suffered by users, and is conducting an investigation through a joint public-private task force," Ryu said. He noted that it is too early to say whether the incident is related to activities by North Korean hackers.

The investigation team, launched Tuesday, discovered that an illegal, unregistered micro base station had connected to KT's communication network. Authorities also asked the two other major telecom operators, SK Telecom Co. and LG Uplus Corp., to check for any illegal base stations on their networks and take precautionary measures. No such devices were found among the two carriers, according to the ministry.

Ryu said investigators will expand their probe to determine how the unregistered base station accessed the network, how the unauthorized payments were processed, and what information may have been compromised. Since Aug. 27, some KT users, mostly in southwestern Seoul, have reported unauthorized mobile transactions. KT said it has blocked all unusual payment requests since Friday.