More than 230,000 Japanese people listed as 100 years old cannot be located and many may have died decades ago, according to a government survey released today.

The justice ministry said the survey found that more than 77,000 people listed as still alive in local government records would have to be aged at least 120, and 884 would be 150 or older.

The figures have exposed antiquated methods of record-keeping and fuelled fears that some families are deliberately hiding the deaths of elderly relatives in order to claim their pensions.

The nationwide survey was launched in August after police discovered the mummified corpse of Sogen Kato, who at 111 was listed as Tokyo's oldest man, in his family home 32 years after his death.

Kato's granddaughter has been arrested on suspicion of abandoning his body and receiving millions of yen in pension payments after his unreported death.