A former Asahi Shimbun reporter who has sustained a spate of personal attacks relating to his coverage of so-called "comfort women" years ago says the threats against him are growing worse.

Takashi Uemura said the assault against him and Hokusei Gakuen University in Sapporo, where he works as a lecturer, has escalated to the point that even his 17-year-old daughter, whose mother is a South Korean, is facing death threats.

A threatening letter the president of the university received in early February read: "I will kill his (Uemura's) daughter without fail. I will kill her no matter how many years might take. I will kill her at any cost."