Seoul's foreign ministry expressed "deep concerns and regrets" over a visit to the Yasukuni shrine by a group of Japanese lawmakers.
The ministry reiterated that the international community can trust Japan only when it faces the past and shows sincere self-reflection on history.
Japan's Kyodo News reported that a cross-party group of lawmakers went there on Tuesday, led by Hidehisa Otsuji of the main ruling Liberal Democratic Party.
Lawmakers had suspended these visits in the past two years due to the pandemic.
The controversial shrine honors Japan's war dead, including Class A war criminals.
Visits to the site are seen as glorification of Japan's past militarism.