Prime Minister Shinzo Abe denounced a top South Korean lawmaker's comments about Emperor Akihito as "extremely inappropriate," ratcheting up already high tensions between the two neighbors.

Abe told the Diet on Tuesday that Japan asked South Korea to apologize for National Assembly Speaker Moon Hee-sang's remarks last week describing Emperor Akihito as "the son of the main culprit of war crimes." Moon made the statement in a Bloomberg interview Thursday in which he urged an imperial apology to resolve a dispute over the "comfort women."

The term comfort women is a euphemism used to refer to women who provided sex, including those who did so against their will, for Japanese troops before and during World War II.