A Cabinet minister and at least 80 other Diet members visited Tokyo's controversial Yasukuni Shrine on Friday.
The Shinto shrine, which honors several Class-A war criminals as well as Japan's war dead, is currently holding its annual spring festival.
The lawmakers' visit follows a series of demonstrations in China that have been linked to Koizumi's repeated visits to Yasukuni, along with the approval of textbooks criticized for glossing over Japan's wartime atrocities.