The computer networks of three major South Korean TV stations and two banks were crippled on Wednesday. According to the country's national news agency, Yonhap, the South Korean police are reviewing all possibilities, including a cyber-attack.

A key presidential official was reported as saying that Seoul is also working to determine whether North Korea was involved in the incident. However, the official added that the attackers' identity and the origin of the attacks have so far not been established. The national news agency reports that the incident affected computer systems at TV stations KBS, MBC and YTN, as well as Shinhan and Nonghyup banks.

Although no government networks have been affected by the attacks, South Korea's military said that it has upgraded its "Information Surveillance Status" by a level. Reportedly, Seoul's telecom operators said that hacking was the suspected cause because of the unusual simultaneous network crashes at several broadcasters and banks. South Korea has accused North Korea of targeting its national networks via cyber-attacks on several occasions in the past. North Korea has always rejected the accusations.