South Korea is speculating that the North was behind a cyberattack that paralyzed the systems of several banks and television stations on Wednesday.

According to state-run South Korean Yonhap news agency, three broadcast companies -- KBS, MBC, YTN -- and two banks, Shinhan Bank and Nonghyup, all reported to the National Police Agency that their networks went down at around 2 p.m. for undetermined reasons.

When the likely attack occurred, images of skulls appeared on some computer screens along with a short message claiming the start of “our movement” from the previously unheard-of “WhoisTeam” group.

Whether or not North Korea is behind the attacks is unclear, but Yonhap reported that the government is investigating the “possibility of North Korea’s involvement.”

South Korea’s watchdog agency responded by tripling staff surveillance and raised the cyberattack alert system to level three on a five-level scale, but the group behind the hack will likely be undetermined for few days.

China, North Korea’s main ally, has been accused of cyberattacks on commercial and governmental entities in the United States. After vehemently denying any government involvement in the widespread attacks in the U.S., China pointed the finger back at America, claiming its systems too have been breached. China has been vocal about protecting national cyberspace and information since the accusations, and continues to stand by its position.

“China would like to work with other countries based on mutual respect and mutual trust in constructive cooperation in this field,” Hong Lei, China’s foreign ministry spokesman, said in a briefing regarding the South Korean hacks.

As relations between the two neighboring countries, still technically at war, deteriorate, North Korea’s involvement in the hack is considered by many a foregone conclusion. This most recent attack on the South’s systems comes just days after the North accused South Korea and its chief ally, the United States, of staging a cyberattack that shut down North Korean websites for two days last week.

Even though relations between Beijing and Pyongyang have become strained after North Korea’s most recent nuclear test in March, China still hopes to use its influence to bring peace to the Korean peninsula.

In a phone call to South Korea’s new President Park Geun-Hye, China’s new president, Xi Jinping, said that he was willing to help promote “reconciliation” between Seoul and Pyongyang.

However, the AFP is reporting that North Korea has been strengthening its cyberwarfare power by creating a tech-savvy unit of an estimated 3,000 people “handpicked for their computer literacy.”