A daughter of Russian opposition leader Boris Nemtsov says Vladimir Putin must bear responsibility for his murder.
Zhanna Nemtsova told the BBC she believed the Russian president was "politically" to blame.
Mr Nemtsov, a former deputy prime minister and veteran liberal politician, was shot dead on 27 February while walking with his girlfriend near the Kremlin.
President Putin has condemned the murder and vowed to find the killers.
Meanwhile, one of the men charged over the murder has said he was forced into a confession.
Zaur Dadayev told prison visitors that he was tied up for two days with a bag on his head, and only confessed to the killing so that a friend would be freed.
'Everybody is frightened'
Speaking to the BBC's Gabriel Gatehouse, Ms Nemtsova echoed previous claims made by her father's allies that his killing was politically motivated.
"He was the most prominent critic of Putin. He was the most powerful leader of the opposition of Russia," she said.
"After his death the opposition is beheaded and everybody is frightened," she added.
"Now we do not have any other figure so powerful... with so much expertise and experience to confront the officials."
The 30-year-old, who is a stock market analyst and TV presenter at a financial channel in Moscow, said she had not been contacted by Russian investigators because they were "not interested in an independent investigation".
Officials have yet to cite a motive for Mr Nemtsov's murder.
Last year, he contacted the Russian authorities after receiving death threats on his Facebook page, which he linked to his position on the conflict in Ukraine.
He had been drafting a report expected to expose covert Russian military involvement in the conflict.
Police turned down his request for an investigation in September.
Ms Nemtsov said she had not been able to access her father's apartment where he kept his files.
Speaking about the moment she learned of the 55-year-old's death, she said: "I couldn't believe it, I still can't believe it.
"They have killed my father, I cannot keep silent."
The EU foreign affairs chief, Federica Mogherini, has called for a "full and transparent" investigation into the murder.
The European parliament is expected to adopt a resolution condemning the killing and the state of democracy in Russia later on Thursday.
On Sunday, a court in Moscow said Zaur Dadayev, who was charged alongside fellow Chechen Anzor Gubashev, had admitted involvement in the shooting on a bridge.
But a member of Russia's human rights council, who visited the suspects in prison on Tuesday, said there were "reasons to believe Zaur Dadayev confessed under torture".
Andrei Babushkin said Mr Dadayev had shown him marks from handcuffs and ropes around his legs, and told him he had been tortured with electricity.
- Zaur Dadayev: Served as deputy commander in Chechnya's North Battalion, part of the regional interior ministry. Chechnya's leader Ramzan Kadyrov described him as one of the unit's "most fearless and courageous members"
- Anzor Gubashev: Zaur Dadayev's cousin and the only other suspect to have been charged. Russia's state TV suggested he might have been the gunman in Mr Nemtsov's murder
- Shagid Gubashev: Anzor Gubashev's younger brother. He says they were detained after hearing of Mr Dadayev's arrest and travelling to Malgobek, a city in the republic of Ingushetia. He claims they are innocent
- Khamzat Bakhayev and Tamerlan Eskerkhanov: Little is known about them but they were reportedly arrested in Moscow and deny any involvement
He called for "people not involved in the investigation" to look into the claim.
Three other men, including Mr Gubashev's brother Shagid, are being held in connection with the case.
Russia's investigative committee said Mr Babushkin and a journalist accompanying him had been allowed to visit the prison to inspect the confinement conditions.
But they went beyond their remit by inquiring about the criminal case, violating "not only the established norms, but the law," a statement said.
Both Mr Babushkin and journalist Eva Merkacheva would be questioned by investigators, the committee said.
People close to Mr Nemtsov have cast doubt on suggestions he might have been targeted because he had defended the publication of cartoons of the Prophet Muhammad by the French satirical magazine Charlie Hebdo.
They said he was not prominent critic of radical Islamism and focused his criticism on President Putin.
You can watch the full BBC2 Newsnight interview on BBC iPlayer.