The Investigative Committee of Russia completed an additional criminal investigation against the Khachaturian sisters accused of killing their father.

Investigators have refused to drop a murder charge against the sisters, BBC reported.

Russian general prosecutor's office concluded earlier this year that the sisters had been subjected to prolonged physical and sexual abuse.

The killing should, therefore, be seen as 'necessary self-defence', the office said.

According to BBC, that ruling was expected to close the case, "but a lawyer for one of the women has told the BBC that Russia's investigative committee has now rejected the prosecutor's position."