For the first time since taking office, Japanese Prime Minister Fumio Kishida has sent a ritual offering to the controversial Yasukuni Shrine, a site viewed by Japan's neighbors, including both Koreas, as a glorification of the country's past militarism.
Japanese media report that Kishida sent a "masakaki" tree on Sunday for the start of the shrine's two-day autumn festival.
The shrine honors Japan's war dead, including 14 Class A war criminals, so visits there are highly provocative.
Responding in a statement, the South Korean government expressed disappointment, and called for the Japanese government to face historical facts and show sincere remorse.
To avoid worsening diplomatic tensions, Prime Minister Kishida did not go to the shrine in person.
But his immediate predecessor Yoshihide Suga, who resigned early this month, did go on Sunday.
The last sitting Japanese PM to visit was Shinzo Abe in December 2013.