South Korea has decided not to attend a memorial ceremony set to take place in Japan to honour wartime forced labour victims, including many Koreans, its foreign ministry said on Saturday, citing unspecified disagreements with Tokyo.

The East Asian neighbours have long been at odds over historical issues linked to Japan's brutal colonial occupation of the Korean peninsula from 1910 to 1945, including sexual slavery and forced labour.

In July, a network of mines on a Japanese island infamous for using conscripted wartime labour was added to Unesco's World Heritage register, after South Korea voiced objections to its listing.

Seoul had dropped its initial objections "on the condition that Japan faithfully implements the recommendation... to reflect the 'full history' at the Sado Gold Mine site."

Tokyo had agreed to host a memorial event every year – its first edition set to be held on Sado Island on Sunday – to honour the forced labour victims, as a condition for South Korea's consent to the Unesco listing.

But on Saturday, Seoul said the country would "not attend the Sado mine memorial ceremony, scheduled for November 24, taking into account various circumstances surrounding the event."

"There was insufficient time to reconcile differing positions between the diplomatic authorities of both countries, making it unlikely to reach a mutually acceptable agreement before the ceremony," it added, without elaborating further.

Tokyo said earlier this week that Akiko Ikuina, a parliamentary vice minister at Japan's foreign ministry, will attend the ceremony as the government's representative, according to Seoul's Yonhap news agency.

The announcement was met with criticism from some local media outlets in Seoul, as she has visited the Yasukuni Shrine – a site considered highly sensitive in South Korea due to the enshrinement of some of Japan's war criminals there. (AFP)