Photo shows Tu's letters auctioned online. (Photo/Beijing Youth Daily)

Tu Youyou's handwritten inscription. (Photo/Beijing Youth Daily)

Three personal letters of Nobel prize winner Tu Youyou and her handwritten inscriptions have been on sale in an online auction since Tuesday.

Starting at 10 yuan, the highest bid for the letters has reached 25,205 yuan ($3,900) as of 10 pm yesterday night, while the bid of Tu Youyou's handwritten inscription has reached 4,000 yuan ($630).

When receiving the interview from Beijing Youth Daily, Tu Youyou said that she was unaware of the issue, and she doesn’t consent to the auction. However, she is too busy to deal with the issue.

The three letters are addressed to the late Chinese pharmacologist Song Zhenyu. According to the seller, the letters are absolutely authentic. They were among the belongings of Song that he bought five years ago. He has acquired them at almost "zero cost".

Kang Kai, lawyer from Beijing Yinoke Law Firm said that Tu owns the copyright to the letters. Without the consent of Song and Tu, the seller has no right to auction Tu's letters.

On October 5 Chinese scientist Tu Youyou won the Nobel Prize in physiology or medicine amongst a trio for discovering anti-parasite therapies. Together, the three scientists found “therapies that have revolutionized the treatment of some of the most devastating parasitic diseases”. 85-year-old Tu was awarded this world-renowned prize for her contribution to reducing the death rate of malaria, minimizing patients’ suffering and promoting mankind’s health.