KOBE (Kyodo) -- Akihiro Arimoto, the father of a Japanese woman abducted by North Korea in 1983 who strenuously fought for her return and that of the other victims, has died without seeing his daughter again, his family said Monday. He was 96.

Arimoto's daughter Keiko was taken to North Korea at age 23 after traveling to study in London. His death early Saturday due to natural causes comes with little progress on the return of Japanese nationals who were abducted by North Korea in the 1970s and 1980s.

Prime Minister Shigeru Ishiba told a parliamentary committee that Arimoto's death was "truly regrettable," adding the government "will use every available means to repatriate abduction victims as soon as possible."

Sakie Yokota, the 89-year-old mother of iconic abductee Megumi Yokota and part of a group representing families of the abductees, expressed her sadness at a press conference.

Now the only surviving parent of an individual listed by Japan as having been abducted by North Korea, Yokota pledged to "continue to do everything I can while I am alive."

Arimoto and his wife Kayoko, who died aged 94 in 2020, campaigned for their daughter's return. He helped found the group for families of the abductees in March 1997 and served as its deputy representative.

He also spoke across the country with other relatives of the abductees and gathered support through petitions. He met with Donald Trump in 2017 and Joe Biden in 2022 during the U.S. presidents' visits to Japan, seeking their cooperation in resolving the abduction issue.

The Japanese government officially lists 17 abductees, five of whom were repatriated in 2002 after a visit to Pyongyang by then Prime Minister Junichiro Koizumi.

North Korea said in 2002 that eight of the individuals, including Keiko, had died and the four others never entered the country. But Arimoto repeatedly said his daughter was alive in North Korea.