Ohmynews's influence was highlighted after an American military armored vehicle ran down and killed two South Korean schoolgirls last June.

While the accident attracted relatively little attention in the mainstream press initially, Ohmynews was aggressive in its coverage. The stories prompted one "citizen reporter" to call for protests.

The idea snowballed and South Korea experienced some of its largest anti-U.S. demonstrations in years and calls for a review of the U.S.-South Korea military alliance.

Mainstream newspapers later criticized Ohmynews, questioning whether it was ethical for a so-called reporter to incite demonstrations.

The fast rise in popularity of Ohmynews, and other online news services, is partly attributable to South Korea's high Internet use. About 70 percent of homes have high-speed broadband Internet access connections -- more than anywhere else in the world.

Paik Hak-soon, a political analyst at the Sejong Institute research center, said "the mainstream press still has the ear of the majority of the public. But things are changing."

"Twenty- and 30-year-olds are getting their news from the Internet," he said.