Tokyo has asked the Australian government to release a 69-year-old Japanese man serving a 15-year prison sentence in Melbourne for drug-smuggling due to poor health, Foreign Minister Yoriko Kawaguchi said Friday.

"This person has said he has become physically weak, that life in prison is very painful and that he has reached his psychological limit," Kawaguchi said. "He has asked us to make a request to the Australian government to allow him to return to Japan.

"Considering his old age, we have asked (Australia) to release him as soon as possible from a humanitarian standpoint," she said at a news conference.

The man, whose name was not provided, is among a group of five Japanese sentenced to prison in 1994 for drug-smuggling after customs agents discovered some 13 kg of heroin concealed in their suitcases when they arrived at Melbourne airport from Kuala Lumpur in June 1992.

They claim they did not know anything about the drugs and that the suitcases were provided to them by locals in Kuala Lumpur after their own suitcases were stolen and later found badly damaged, according to their supporters.