Shinhan Bank
A pedestrian walks past a branch office of Shinhan Bank in central Seoul August 3, 2011. Reuters/Truth Leem

South Korean authorities are investigating network outages that hit the nation’s key broadcasters and banks Wednesday, paralyzing their operations in a suspected cyber attack.

At least three broadcasters — KBS, MBC and YTN — and two banks — Shinhan Bank and Nonghyup — reported to the National Police Agency that their computer networks were entirely halted around 02:00 p.m. local time (05:00 a.m. GMT) for unknown reasons, Seoul’s Yonhap news agency reported citing police.

South Korean Internet service provider LG UPlus said it believed its network had been hacked, which led to an outage causing the networks of the broadcasters and the banks to fail, Reuters reported.

The Korea Internet and Security Agency (KISA) immediately launched an investigation to establish the cause.

“The response center is working on the cause of the computer networks of broadcasters going down,” a KISA official told the Korea Herald. The authorities did not immediately rule out North Korea’s involvement, the report added.

However, KISA said it is yet to find any evidence of external attacks, YTN stated.

Allegations of cyber attacks by both the Koreas against each other are not uncommon.

North Korea was accused of launching cyber attacks on South Korean organizations including government websites and media outlets, last year. Pyongyang was the alleged perpetrator behind the hacking Nonghyup computer networks, several other businesses and the email accounts of Korea University in 2011, according to Korea Herald.

The attack came amid Pyongyang’s increasingly belligerent rhetoric against South Korea and the U.S. and days after it accused the two nations of cyber attacks on its Internet servers.

Official sites of KCNA, Air Koryo and Rodong Sinmun, the party newspaper, were reported to have been inaccessible on some occasions in mid-March.

Russia's Itar-Tass news agency said a "powerful hacker attack" from abroad had brought down Internet servers inside the North, deeming some websites inaccessible.

Pyongyang’s official news agency KCNA said Mar. 15 it was "nobody's secret that the U.S. and South Korean puppet regime are massively bolstering up cyber forces in a bid to intensify the subversive activities and sabotages against the DPRK [North Korea].”