South Korean police said Friday they have launched an investigation after a visitor from Japan was found to have used several hundred counterfeit 10,000 yen bills at a casino in Seoul.

The man, an ethnic Korean who runs a real estate business in Japan, exchanged 420 bogus 10,000 yen bills at a hotel casino Friday, according to police.

The man was quoted as claiming he did not know the bills were fake.

The bills were part of 15.2 million yen in cash that the man, who entered South Korea on Tuesday for the purpose of gambling, exchanged at the hotel's casino.

They were discovered when someone at the money exchange desk, suspecting some of the bills were fake, requested a bank authentication.

It is not known whether the incident is connected to the recent spread of fake 10,000 yen bills in Japan. It was the largest number of fake 10,000 yen bills found in a single incident since the use of hundreds of fake bills came to light in Japan over the holidays.