The foreign ministry says it had requested Japan to put on display materials that include the expression "forced labor" in an exhibition of Japan's Sado mines but Tokyo had rejected the call. 

In a reply submitted to main opposition Democratic Party Rep. Lee Jae-jung on Tuesday, the ministry said it had made such a request in the process of negotiating the materials that would be in the exhibition at Aikawa Folk Museum, located five kilometers away from the mines.

The exhibition opened last Sunday, just a day after the mines were designated as a UNESCO World Heritage Site. 

Meanwhile, the ministry’s spokesperson Lee Jae-woong said in a regular briefing that the ministry will thoroughly review the statement released by National Assembly speaker Woo Won-shik and provide necessary explanations to parliament. 

Earlier in the day, Woo released a statement in which he urged the government to reveal all diplomatic negotiations it had held with Japan on the Sado mines as he expressed deep regret over Seoul agreeing to the UNESCO World Heritage registration of the mines.