SEOUL, South Korea -- More than 220,000 South Koreans have been victims of online identity theft in connection with a popular Web-based game, the site's operator said Monday.

The case reveals the growing problems with information protection in the world's most wired country.

The victims filed complaints with the operator of the Web-based fantasy game Lineage in the past week after discovering they had accounts for the game without their knowledge, the Seoul-based game company NCSoft said.

The complaints began after media reported last week that about 600 people had Lineage passwords they hadn't signed up for. Hearing the news, other people checked the Web site to see if their identities were being used.

To sign up for a game account, Internet users must provide their name and resident registration number, which is the main form of national identification.

Police are investigating who stole the personal information. But local media have speculated on involvement by Chinese trying to make money by selling virtual weapons and abilities used in the game.

The game is based around the story of a prince and five knights fighting to regain a lost throne. As players progress through the game, they can win special abilities, called "items," which can be sold to other online players.

It's not illegal to sell these virtual items, but NCsoft says it warns users not to do or risk suspension from the game.

Still, such deals are believed to be widespread and there have been reports of physical violence over disputes surrounding such transactions.

In China, there are rings of talented gamers who win Lineage items by playing the game and then sell them for money, according to NCsoft. But the Chinese gamers need personal information of South Koreans as only Koreans can register at the Korea-based Web site.

While Lineage is also played in other countries, such as the United States and China via different servers, the bartering of such items is most active among Korean users.

The case has raised concern that such leaked personal information could be used for more serious crimes, although there have been no reports of financial losses from stolen personal information in the Lineage case.

The scandal has awakened South Korea -- with the highest per-capita rate of broadband connections in the world -- to the need for better precautions against online information leaks.

South Korean firms have been criticized for demanding too much personal information from customers for online transactions while not protecting them properly.

According to the state-run Korea Information Security Agency, 33,000 cases of computer network hacking were reported in the country last year. But officials said the actual number is likely much larger as many cases go unnoticed.