Japan is facing growing demand that it make more efforts to shed light on its dark history related to an island where many Korean workers were forced into labor during World War II.

Hashima Island, located off the Japanese city of Nagasaki's coast, was added to the UNESCO World Heritage list in July 2015 for industrial sites used decades ago.

South Korea voiced protest against the move as its people were forced onto the uninhabited island in the 1940s to work in coal mines there. UNESCO recommended Tokyo include a "full history" related to those facilities.

An official from Japan's Cabinet Secretariat recently told Yonhap News Agency that the government is considering ways on how to explain the world heritage sites based on opinions from experts.

His comment was a response to a question raised about preparations that have been made to more fully explain the island's history as the first anniversary of it being added to the heritage list approaches.

The official added that explanations about the fact that there was a policy for forced labor existed will be included. He said that the efforts will be made in recognition of harsh conditions under which Korean laborers had to work decades ago.

He, however, noted that the deadline for Japan to submit its "follow-up measures" after the designation is more than a year away, hinting that Tokyo will not be in a hurry to make any decisions on what explanations about forced laborers will be included.

Tokyo has been under criticism for changing its stance and promises related to the island.

A Japanese representative made a speech last year at a World Heritage committee meeting in which he apparently admitted there was coercion involved in bringing workers to the island. Japan later denied acknowledging that there was any coercion involved.

Tokyo has become ambiguous in dealing with the issue ever since, with some media outlets even causing fresh controversy by apparently trying to dilute historical facts.

A Japanese media report earlier said that the city of Nagasaki had distributed a document to the department in charge of tourism in which it explained the life on the island was like any other "coal mine community" and people there were like a "family."

A Seoul government report released years ago showed that around 120 Koreans were confirmed dead after being forcibly taken to work in the coal mines on the island also known as Battleship Island as it looks like a battle ship.

Japan has been asked to submit its implementation report on how it has carried out the recommendations made by UNESCO no later than Dec. 1, 2017.  (Yonhap)