China and South Korea have condemned Japanese Prime Minister Shinzo Abe for visiting a shrine that honours war dead including convicted war criminals.
Seoul said it was furious with the "deplorable" act, and Beijing labelled the visit "absolutely unacceptable" and summoned Japan's ambassador.
Japan's neighbours see the Yasukuni shrine as a symbol of the militarism of Japan during and before World War Two.
US officials said the visit would "exacerbate tensions" in the region.
China, Japan and South Korea are embroiled in a number of disputes over territory in the East China Sea.