SEOUL, South Korea — Several North and South Korean websites that went offline on a war anniversary remained shut down Wednesday, a day after what Seoul partly blamed on a hacking attack.
The shutdown appeared to be less severe than one in March, and some government and private sector sites were operating again.
The main page of the presidential Blue House was restored, but websites for the prime minister's office, the science ministry and South Korea's spy agency remained offline. The conservative South Korean newspaper Chosun Ilbo was back online.
North Korea's national airline, the Rodong Sinmun newspaper, the North's official Uriminzokkiri site and Naenara, the country's state-run Internet portal, had been shut down Tuesday, and all but Air Koryo were operational a few hours later.
Seoul blamed hacking for the shutdown of the South Korean sites, and National Intelligence Service officials said they were investigating what may have shut down the North Korean websites. North Korea has not commented.
The shutdowns occurred on the 63rd anniversary of the start of the Korean War, which both countries commemorated. They also are preparing for the 60th anniversary of the end of the fighting July 27, a day North Koreans call "Victory Day" even though the Korean War ended in a truce, not a peace treaty.
It wasn't immediately clear what or who was responsible for the shutdowns. Several Twitter users purporting to belong to the Anonymous hackers' collective claimed they attacked North Korean websites, but they did not respond to attempts by The Associated Press to communicate with them. Shin Hong-soon, an official at South Korea's science ministry in charge of online security, said the government was not able to confirm whether these hackers were linked to the South Korean attacks.
North and South Korea have traded accusations of recent cyberattacks.
A March 20 cyberattack struck 48,000 computers and servers in South Korea, hampering banks and broadcasters for several days, though it did not interrupt television programming or compromise bank records or personal data. Seoul has pointed to a North Korean military-run spy agency as the culprit.
North Korea blamed South Korea and the United States for cyberattacks in March that temporarily disabled Internet access and websites in North Korea.
Experts believe North Korea trains large teams of cyber warriors and that the South and its allies should be prepared against possible attacks on key infrastructure and military systems. If the inter-Korean conflict were to move into cyberspace, South Korea's deeply wired society would have more to lose than North Korea's, which largely remains offline.
Thousands of North Koreans gathered Tuesday evening in Pyongyang's main Kim Il Sung Square for the largest of many rallies around the nation denouncing the United States. People held signs calling for "Death to the U.S. imperialistic aggressors."
On Monday evening, men lined up in the shadow of the capital's iconic Juche Tower to practice coordinating their steps as they hoisted signs reading "sworn enemies," and "U.S. troops out of South Korea" while a man with a megaphone barked orders.
In South Korea, thousands of people, including Korean war veterans, gathered at Jamsil Stadium in Seoul. Two South Korean army units held military drills in Yeoncheon in Gyeonggi Province, near the demilitarized zone, defense officials said in Seoul.
North Korea in recent weeks has pushed for diplomatic talks with Washington. Tensions ran high on the Korean Peninsula in March and April, with North Korea delivering regular threats over U.N. sanctions and U.S.-South Korean military drills.