Several government and private sector websites in South Korea were hacked this morning, including the site for the Cheongwadae, the country’s presidential residence, reports the AP. The attacks come on the 63rd anniversary of the start of the Korean War, but it’s not yet clear who is behind them. According to South Korea’s Chosun newspaper, the Cheongwadae site displayed a slogan voicing support for North Korean leader Kim Jong-un earlier today, although now it only shows a page (pictured above) advising visitors of a "temporary halt in operation" due to a "system check."

In March, several of South Korea’s banks and TV networks were affected by a massive malware attack, crippling ATMs and online banking. The country had blamed North Korea for the attack, but Pyongyang has denied any involvement.

Some are looking at Anonymous Korea, whose Twitter account indicates that its members attacked multiple North Korean websites today, including the official government website korea-dpr.com, following through on plans it announced back in April. However, the group denies any role in today’s attacks on South Korean targets, says Chosun.

The AP writes that South Korea’s science ministry alerted citizens to the attacks on government websites and media servers earlier today, encouraging officials and others to beef up their network security.

Hyunhu Jang contributed to this report