Japan Post said Thursday it "carelessly" issued customized stamp sheets featuring images of Takeshima Island, which is claimed by Japan and South Korea.
Japan Post issued 300 sheets, which are used to hold regular stamps, bearing a Takeshima theme as ordered by a retailer of stamps and coins between January and February, the government-backed corporation said.
The dispute over the island, known as Tok-do in Korean, flared recently when South Korean postal authorities issued Tok-do stamps on Jan. 16, despite objections from Japan.
The design of the sheets in question features a photographic image of the island and the word "Takeshima" in English and kanji.
In February, Japan Post rejected a request by a Tokyo man seeking sheets of this kind.
"This time, post offices carelessly granted the request," a Japan Post official said, referring to the Tokyo Central Post Office and another post office in Shinjuku.
Earlier, a group of Liberal Democratic Party lawmakers publicized a plan to place an order with the Tokyo Central Post Office on Friday to print customized stamp sheets featuring the island.
Apparently mindful of the lawmakers' imminent request, Masahiro Tabata, senior vice minister at the Public Management, Home Affairs, Posts and Telecommunications Ministry, told a news conference Thursday, "It would be ridiculous if Japan Post, which granted those requests, turns down a similar request."
Mostly a cluster of small reefs, Takeshima is uninhabited.