Updated

North Korea runs a cyberwarfare unit that tries to hack into U.S. and South Korean military networks to gather confidential information and disrupt service, a news report said Tuesday.

The North's military has expanded the unit, staffing it with about 100 personnel, mostly graduates of a Pyongyang university that teaches computer skills, Yonhap news agency reported, citing an intelligence agency it didn't identify.

South Korea's Defense Ministry said it is aware that Pyongyang has been training hackers in recent years but did not provide details and had no other comment.

The National Intelligence Service — South Korea's main spy agency — said it could not immediately confirm the Yonhap report.

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The report came a day after the Defense Ministry said it had signed an accord with the Pentagon to strengthen their cooperation in fighting against cyber threats. The ministry statement, however, did not identify any specific cyber threats, such as from North Korea.

The U.S. stations about 28,500 troops in South Korea as a deterrent against North Korea. The U.S. military command's public affairs office in Seoul was not immediately available to comment on the report Tuesday, a national holiday in South Korea.

North Korea — one of the most secretive countries in the world — is believed to have a keen interest in information technology.

The country's absolute leader, Kim Jong Il, has pushed for further development of advanced computer technology, saying those who don't use computers are among the "three main fools of the 21st century" along with those who smoke and don't appreciate music.

But North Korea tightly controls access to computers and the Internet for ordinary citizens. South Korea, in contrast, has one of the world's highest per capita rates of broadband Internet connection.