TOKYO -- The South Korean national team lodged a complaint with the organizers of the World Baseball Classic (WBC) after a Japanese fan brought his country's imperial-era flag to a game between South Korea and Japan here Friday.

The Rising Sun Flag was seen in the upper deck in the left field at Tokyo Dome prior to the Pool B game between the rival nations.

Koreans regard the flag as a symbol of Japan's past militarism, because it was hoisted during Japan's invasion of Asian countries starting in the late 19th century. They also say the Rising Sun Flag is to Asian nations what the Nazi's swastika is to Europeans.

An official with the Korea Baseball Organization (KBO), which governs professional baseball in South Korea, said the KBO lodged a protest after the flag was seen at the dome.

The KBO had previously asked the WBC Inc. (WBCI) and Tokyo's local organizers to ensure there would be no Rising Sun Flags at the Korea-Japan game.

"The WBCI responded at the time that they were aware of the controversy surrounding the flag and they would look into measures to ban the flag," the KBO official said. "Japanese officials had also told us that they would try their best to keep the flag out of the stadium."

Prior to the game, Japanese Prime Minister Fumio Kishida threw out the ceremonial first pitch. South Korean President Yoon Suk-yeol is scheduled to visit Japan next Thursday, the first bilateral presidential trip to Japan in a dozen years.