TOKYO -- The sour state of relations on the Korean Peninsula has led to equally sour relations on the Internet, with North and South Korea now engaged in a micro-battle over micro-blogging.

It started Aug. 12, when North Korea opened a Twitter account, using the popular site to spread propaganda. The South this week responded by trying to block its citizens from accessing the content, threatening offenders with jail. The North, in turn, engineered ways to bypass some of the censorship.

As of Friday, South Korean Internet users who sought out the North's Twitter page instead received a warning from the Korea Communications Standards Commission saying that the site had been banned because of "illegal content."

"The current measure is working effectively enough," said Han Myeong Ho of the agency's illegal-information review division. "But various ways need to be reviewed to completely block access to North Korean accounts."

Using the Twitter name uriminzok, Pyongyang has ventured into the social-media world, mostly by tweeting links to a Web site that vilifies South Korean and U.S. policies, provides official state news accounts and occasionally details modernization work at factories. One Twitter-linked story Thursday mentioned that Kim Jong Il had sent food to two women celebrating their 100th birthdays.

On Friday, in another twist, North Korea used a link on its Twitter account to redirect Internet users to an apparently related Facebook page. The Facebook account, Uriminzokkiri -- roughly "our nation" -- has prompted South Korea to investigate it; if it is confirmed as a North Korean account, it will be blocked.

Seoul has confirmed that the Twitter account, which now has more than 9,000 followers, is operated by an official arm of the Korean Workers' Party. The South Korean government's response to Pyongyang's propaganda feed contrasts sharply with U.S. receptiveness. On Tuesday, State Department spokesman P.J. Crowley wrote on his own Twitter page, "We use Twitter to connect, to inform, and to debate. We welcome North #Korea to Twitter and the networked world." He also wrote, "The North Korean government has joined Twitter, but is it prepared to allow its citizens to be connected as well?"

In Pyongyang, only the most privileged citizens have access to the Internet. "For most North Koreans, 'Twitter' is a word from the moon or Venus," said Young Howard, president of Open Radio for North Korea, a Seoul-based group with contacts in the North.

But North Korea is also believed to maintain a group of master programmers and hackers. South Korea has a cyber defense team that monitors hacking threats from the North.

Under its stringent National Security Law, the South Korean government gives itself the right to ban access to pro-communist information. Already, Seoul blocks several dozen pro-North Korean or North Korean-run Web sites, though that does not apply to the North Korean YouTube channel, which launched about a month ago. According to the Associated Press, South Korea's Ministry of Unification warned earlier this week that South Korean citizens could face punishment for "retweeting" or replying to North Korea's Twitter messages.

"Personally, I am very skeptical of South Korean policy to block all Web sites of North Korea," Howard said. "We are a democracy. We don't have to do this."

North Korea has conducted its social media propaganda strictly in Korean. This week, Pyongyang's Twitter persona also spawned a parody -- Fake_Uriminzok.

On Friday, Fake_Uriminzok wrote, "the dear leader has decided to challenge US devil-leader #Barack Obama to a game of 1-1 basketball at his palace in Pyongyang."

Special correspondent Yoonjung Seo contributed to this report.