The office of the Chief Cabinet Secretary made the poster claiming that Dokdo is Japan's native territory illegally occupied by South Korea, according to Seo Kyoung-duk, a professor at Seoul's Sungshin Women's University.
The poster titled "Do you know?" also claimed Japan's territorial sovereignty over the Kuril Islands under Russia's control, and the Senkaku (Diaoyudao) Islands which are controlled by Japan but also claimed by China. It also carried photos of those islands.
Seo said the poster can also be found in monorail trains on the island of Okinawa.
The poster is similar in design to the one that was put on walls of subway train stations in Tokyo last year, but is more colorful and carries a more detailed explanation about the country's claims to Dokdo than last year's, the professor said.
Seo said he will make and distribute an online poster debunking the Japanese claims.
South Korea has rejected Japan's claims as nonsense because the country regained independence from the 1910-45 colonial rule after the war and reclaimed sovereignty over its territory, including Dokdo and many other islands around the Korean Peninsula.
The country has kept a small police detachment on Dokdo since 1954.
Japan's claim has long frayed relations between the two countries, along with its attempts to whitewash its wartime atrocities, including its enslavement of Korean women as sex slaves during World War II. (Yonhap)