Update 3:50 a.m. EDT: Major government and media websites in North Korea were also offline for several hours on Tuesday, AP reported, hours after Seoul issued a cyberattack alert following the shutdown of South Korean government sites. Website of North Korea’s state-owned airliner, Air Koryo, and the country’s official website, Naenara, were shut down, along with those belonging to state-run newspapers Rodong Sinmun and Uriminzokkiri, but it remains unclear whether they were subjected to hacking. Rodong Sinmun, Uriminzokkiri and Naenara websites were back online a few hours later, AP said.

South Korea issued a cyberattack alert in response to an apparent hacking attempt on government computer networks on Tuesday morning, news reports said.

The website of the presidential office was among multiple government sites that were taken down by the attack, which coincided with the anniversary of the 1950-53 war between the two Koreas. The attack also hit at least one media website, reports said.

“The government can confirm a cyberattack by unidentified hackers that shut down several sites including the Blue House,” the Science Ministry said in a statement, referring to the presidential office, BBC reported.

Officials said they are investigating the possibility of hacking, and that an alert was meant to caution government and public entities to be vigilant against a potential cyberattack, Associated Press reported.

On March 20, three South Korean broadcasters -- KBS, MBC and YTN -- and two banks -- Shinhan Bank and Nonghyup -- reported cyberattacks on their networks that paralyzed their operations.

South Korean authorities initially traced the March attack to an Internet address located in China, which strengthened early suspicions of North Korea’s hand in the incident, as South Korean intelligence officials believe it is not unusual for North Korea to use Chinese IP addresses to mask its attacks. On April 10, South Korean authorities said an investigation found North Korea was responsible for the March cyberattack.

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