TOKYO—Japanese Prime Minister Shinzo Abe stepped up his campaign to revisit Japan's wartime history, responding to criticism from Asian neighbors with a new round of comments that have further aggravated tensions with South Korea and China.

With emotions running high over visits by members of his cabinet to a wartime memorial, Mr. Abe stoked passions further by appearing to question whether Japan's World War II aggression and occupation of countries around the region could be labeled an "invasion."

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