South Korea commemorated wartime Korean forced laborers at Japan’s Sado gold mines in a ceremony Monday, a day after boycotting a similar event organized by Japan, as tensions over historical atrocities continue to strain relations between the two sides.

South Korea expressed regret to Japan on Monday over Tokyo's attitude towards a memorial service held for labourers including Koreans forced to work in Japan's Sado mines during World War Two, Seoul's foreign ministry said.

SADO, Japan (AP) — Japanese officials on Sunday paid tribute to workers at the country's Sado Island Gold Mines but offered no apology over Japan’s brutal wartime use of Korean forced laborers, highlighting lingering tensions between the neighbors over the issue.

After boycotting one organised by Tokyo, South Korea held its own memorial event on Monday for compatriots forced to work in a Japanese mine during World War Two, highlighting lingering sensitivities between the countries.

South Korea’s government says it has decided not to attend a memorial service near Japan’s Sado Island Gold Mines due to unspecified disagreements with Japan over the event, which stirred longstanding tensions over the abuse of Korean forced laborers at the site before the end of World War II.