World's oldest woman
Misao Okawa (R) receives a certification from an official of Guinness World Records in Osaka, western Japan, in this photo taken by Kyodo on 27 February, 2013. - Reuters

The world's oldest woman in Japan, Misao Okawa, has turned a year older marking her 115th birthday.

Okawa, who lives in the Japanese commercial city of Osaka, celebrated the day in a nursing home eating her favourite mackerel sushi dish.

Appearing on a local television channel, she thanked "everybody" and said she did not expect to see "such a great age".

Only a week back, Okawa received the certificate from the Guinness World Records recognising her as the oldest living woman on earth. She celebrated the occasion with a bowl of mackerel sushi.

Okawa, who was born in 1898 to a clothing merchant, got married in 1919. She presently has four grandchildren and six great-grandchildren. Two of her children are in their 90s.

"On my father's side, there are some who lived long and some who don't - like my father who died at 36 - so I doubt I'll live as long," said one of Okawa's sons, Hirosi during the occasion.

She attributes her longevity to a healthy diet and local reports say she never encountered any major health issue until she was 102. Okawa was confirmed as the oldest living woman following the deaths of Dina Manfredini in the US and Koto Ukubo in Japan in quick succession.

The oldest living person, Jiroemon Kimura, who is also living in Japan, will turn 116 in April. In December he was named the world's oldest ever documented male and is only the third man in history to reach 115 years.

Japan has around 51,000 centenarians and close to 87 percent of them are women, according to government data.