North Korea masterminded a series of hacking attacks that crippled networks of South Korean banks and broadcasters last month, a government official said Wednesday.

Computer networks at three local banks -- Jeju, NongHyup and Shinhan -- and three TV broadcasters -- KBS, MBC and YTN -- were paralyzed on March 20 due to malicious code from the outside.

A probe into access records and the malicious codes showed that Pyongyang's Reconnaissance General Bureau launched the attacks, according to the official.

The South Korean government is set to announce the probe results later in the day. (Yonhap News)