Father of Japanese abductee to North Korea dead at 87

June 5 (UPI) -- The father of a Japanese citizen who was abducted to North Korea as a teenager has died after decades of activism that drew international attention to Pyongyang's secret program of kidnappings.

Shigeru Yokota, father of Megumi Yokota, was 87 when he died of natural causes on Friday, Kyodo News and Jiji Press reported.

Shigeru Yokota and his wife, Sakie Yokota, were involved in activism urging the North Korean government to return all Japanese citizens.

Megumi was 13 when she vanished from her hometown in Niigata Prefecture in 1977. Shigeru at the time was an employee of the Bank of Japan.

Shigeru, like other relatives of Japanese citizens who were kidnapped to the North, suspected victims like his daughter were abducted to the isolated country. The Yokotas formed a group with seven other families in 1997 to raise awareness of their missing relatives. In 2002, North Korea confirmed a past program of kidnapping foreign citizens.

On Friday, Sakie Yokota expressed sadness over the death of her husband.

"My husband and I did our best together, but he passed before seeing Megumi again. I'm at a loss right now," she said in statement.

Japanese Prime Minister Shinzo Abe made the issue of abducted Japanese citizens a focal point of his North Korea policy.

"I'm filled with regret and sadness that as prime minister I have not been able to bring Megumi back to her parents. We must act decisively and take every opportunity to bring her and the other abductees home," Abe said Friday.

The Yokotas never saw their daughter after her disappearance. They did meet with their granddaughter Kim Eun Gyong in Ulaanbaatar, Mongolia, in March 2014.

North Korea has previously claimed Megumi is dead. The Yokotas never disclosed the status of their daughter following the 2014 meeting.