Lucie Blackman was found dead near Tokyo in 2001
Prosecutors in Japan have begun an appeal against the acquittal of the man accused of killing British bar hostess Lucie Blackman.
Joji Obara, 54, was cleared of any involvement in the death of the 21-year-old but was jailed for life for raping nine women, one of whom died.
Miss Blackman, 21, of Sevenoaks, Kent, was found dead near Tokyo in 2001. She had been working as a bar hostess.
The judge said there was no proof Obara alone was responsible for her death.
Lawyers had claimed Obara drugged and raped Miss Blackman before she died, and then chopped up her body and encased her head in concrete.
Tokyo's public prosecutor filed an appeal against the Tokyo District Court ruling on Friday, according to a court spokeswoman.
However, she did not provide any other details and it is not yet clear what part of the ruling prosecutors were appealing.
The Tokyo District Prosecutors' office has refused to comment on the appeal.
It comes after Miss Blackman's family said it would urge prosecutors to appeal.
They said the former flight attendant had been "robbed of her justice".
Last week Miss Blackman's mother, Jane Steare, of Sevenoaks, Kent, said she was pleased there would be an appeal and fully supported it.
She said: "All I have ever wanted is justice for my darling daughter Lucie.
"I believe there are grounds to be optimistic that an appeal will succeed."
Ms Steare is involved in a dispute with Tim Blackman, her ex-husband and Miss Blackman's father, over her claims that he could have undermined the prosecution's case against Obara.
She has criticised him for accepting 100 million yen (£450,000) from a friend of the defendant last year.
Mrs Steare said she and Mr Blackman had both received "unequivocal" guidance that accepting condolence money could lead to a more lenient sentence.
But Mr Blackman argued the payment was not "blood money" and said such "offers of condolence" were common in Japan and did not affect the court case.
On Monday it emerged that police in Britain were investigating an alleged theft of money from a trust in memory of Miss Blackman.
Hampshire Police have written to Mr Blackman asking for an explanation of apparent financial discrepancies.
Mr Blackman said in a statement that there was no case to answer.