SEOUL (Reuters) - 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.

South Korea has paid tribute to wartime Korean forced laborers at Japan’s Sado gold mines in a memorial ceremony.

The top diplomats of South Korea and Japan agreed Tuesday to keep the momentum alive for bilateral cooperation, despite discord over a memorial event for Korean victims of Japan's wartime forced labor,

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.

Japan has held a memorial ceremony near the Sado Island Gold Mines despite a last-minute boycott of the event by South Korea that highlighted tensions between the neighbors over the brutal wartime use

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.

North Korea condemned on Saturday recent joint military drills by the United States, South Korea and Japan, warning that it would take immediate actions if needed to defend the state.

South Korea has paid tribute to wartime Korean forced laborers at Japan’s Sado Island Gold Mines in a memorial ceremony