The head of a Seoul-based association for families of people North Korea has abducted says Shin Sook-ja, widely known as the "Daughter of Tongyeong," and six other abductees are all dead.

Choi Sung-yong cited official documents confirming the deaths of Shin, Han Man-taek, Japanese abductee Yokota Megumi and four others. Choi said Shin died from liver-related disease in November 2008 and Megumi died in December 2004, contrary to the North's claims that she died in April 1994.

Han, who escaped Pyongyang in 2004 but was arrested by China and forcibly sent back to the regime, died in September 2009. The deaths of other abductees such as fishermen Kang Yeo-jin, Lee Ki-ha, Yoon Sam-moon and Park Sang-won were also confirmed.

The Unification Ministry says it is difficult for the government to further investigate the case, as the documents were obtained through an unofficial route.