A wooden plaque showing the name of Japan's PM Abe is seen with a "masakaki" tree that Abe sent as a ritual offering for the war dead at Yasukuni Shrine in Tokyo. Picture: Toru Hanai/Reuters

Tokyo - Japanese Prime Minister Shinzo Abe sent a ritual offering to the controversial Yasukuni Shrine in Tokyo on Saturday, prompting criticism from South Korea.

Abe is expected to refrain from visiting the 149-year-old war memorial during its three-day spring festival from Saturday.

The shrine has been a source of diplomatic tension with other Asian countries as it honours the spirits of Japan's 2.46 million war dead, including 14 Class-A war criminals from World War II.

About 70 Japanese lawmakers visited the shrine on Friday, one day ahead of the festival.

Seoul criticized Abe's move and the lawmakers' visit to the site.

South Korea "expresses its deep concerns and regret over Japanese government and parliamentary officials sending an offering to or visiting the Yasukuni Shrine that glorifies its history of colonial-era invasion and wars of aggression," the South Korean Foreign Ministry said in a statement on Saturday, Yonhap News agency reported.

Seoul urged Tokyo to reflect on and atone for its past deeds and step up efforts to gain trust from neighbouring countries and the international community, the report said.

The Korean Peninsula was under Japanese occupation between 1910 and 1945.

Abe has not offered prayers at the shrine since December 2013, when his visit sparked an international outcry.

Abe's move on Saturday comes six days before the inter-Korea summit between South Korean President Moon Jae In and North Korean leader Kim Jong Un.

Tokyo needs Seoul's help to resolve the kidnapping of Japanese nationals by Pyongyang decades ago.