SEOUL (NYTIMES) - South Korea announced a sweeping crackdown on "fake news" on Tuesday (Oct 2), calling it "a destroyer of democracy".

Conservative critics of the government, however, cried foul, accusing it of trying to impede freedom of speech.

Speaking at a Cabinet meeting, Prime Minister Lee Nak-yon said that fake news had spread so widely in South Korea that it was stymying not only citizens' privacy but also the country's national security and foreign policies, including its relations with North Korea.

Mr Lee did not offer examples.

But he was furious last week after he visited Vietnam for the state funeral for its president, Mr Tran Dai Quang. While in Hanoi, he visited the stilt house of Ho Chi Minh and wrote in the visitors' book at the compound that he felt "humble" before the "great" Vietnamese leader. South Korea fought against his Communist forces alongside the United States during the Vietnam War.

When the photograph of Mr Lee's tribute was reported in South Korea, conservative critics called him a "commie" on social media.

Some even falsely suggested that Mr Lee made the tribute not to Ho but to Kim Il Sung, the founder of North Korea and the grandfather of its current leader Kim Jong Un. Mr Lee has called the misinformation "vicious".

"Fake news is a public enemy hiding behind the cover of free speech," Mr Lee said on Tuesday. "We can no longer turn a blind eye to it."

Mr Lee ordered police and prosecutors to investigate and punish those who "generate fake news with malicious intent and systemically spread it".

He also told the Korea Communications Commission, a government regulatory agency, to act on online media sources that serve as "avenues for fake news".

Mr Lee encouraged government agencies to report fake news to law enforcement authorities for investigation. He also called for a new law regulating such information, which some lawmakers in his Democratic Party had already been advocating.

Opposition lawmakers denounced the government's move as an attempt to silence criticism, especially YouTube videos used by conservative critics to attack the progressive government of President Moon Jae-in, whom they often call a North Korean stooge.

Progressives have long criticised those channels as a main source of inaccurate and unfair information.