SEOUL (Yonhap) — Japan has denied a South Korean singer entry in an apparent retaliation for his recent performance of a song on South Korea’s easternmost islets of Dokdo, also claimed by Tokyo, the singer’s management said Monday.

Lee Seung-chul performed the song “That Day,” featuring Koreans’ long-cherished aspiration for inter-Korean reunification, together with a choir composed of young North Korean defectors in South Korea on Aug. 14, one day before the anniversary of Korean liberation from 1910-1945 Japanese colonial rule.

“Lee arrived at a Japanese airport aboard an Asiana Airlines flight at the invitation of his Japanese acquaintance on Sunday morning but returned home after being held for about four hours at the immigration office for a doubtful reason,” Jin&Won Music Works said.

As a reason for denial, an immigration official allegedly cited unspecified recent media reports about him without elaborating further.

But when the singer said that he would publicly raise the issue of Japan’s “unjust” measure, the official abruptly began to mention Lee’s record of being jailed for smoking hemp 20 years ago.

“The entry denial appears to be a retaliatory measure against Lee’s performance of a song about inter-Korean reunification on Dokdo in August and ensuing domestic news reports about the event,” the agency said.

Japan has never banned him from entry although he visited the country 15 times after the hemp incident, it said, adding that the singer even had concerts in Japan in the early 2000s.

It said the Japanese official found no words to properly explain when asked why the immigration office held Lee’s wife together with him.

Dokdo has been a recurring source of South Korea’s diplomatic tensions with Japan with the neighboring country often renewing territorial claims to the set of islets.

In 2012, South Korean actor Song Il-gook was banned from entering Japan after participating in a relay swimming event to Dokdo in protest of the Japanese claims over the islets.