Russian President Dmitry Medvedev has expressed "outrage" at the murder of a prominent human rights activist, Natalia Estemirova, BBC reported.
He has ordered an inquiry into the killing of Ms Estemirova, who was investigating alleged abuses by government-backed militias in Chechnya.
She was abducted and bundled into a van as she left her home in the Chechen capital, Grozny, on Wednesday.
Her body was found in neighbouring Ingushetia, with gunshot wounds.
Ms Estemirova, 50, had been gathering evidence - for the Russian human rights organisation, Memorial - of a campaign of house-burnings by government-backed militiamen.
The pro-Moscow Chechen president, Ramzan Kadyrov, said the perpetrators of the murder "deserve no support and must be punished as the cruellest of criminals", according to Russian news agency, Interfax.
But the chairman of Memorial, Oleg Orlov, has already accused Mr Kadyrov of involvement in the killing.
In a statement on its website, he said: "I know, I am sure of it, who is guilty for the murder of Natalia...His name is Ramzan Kadyrov."
Mr Orlov alleged that Mr Kadyrov, a former Chechen rebel turned Kremlin ally, had previously threatened Ms Estemirova, and considered her "a personal enemy".
Memorial is one of Russia's best known human rights groups.
In Washington, the White House issued a statement saying the US was "deeply disturbed and saddened by the... brutal slaying".
"Such a heinous crime sends a chilling signal to Russian civil society and the international community and illustrates the tragic deterioration of security and the rule of law in the North Caucasus over the last several months," said the White House.
Ms Estemirova had worked with the activists Anna Politkovskaya, who was shot dead in 2006, and Stanislav Markelov, who was killed in January this year.
In 2007 she was awarded the inaugural Anna Politkovskaya Prize, and had also received awards from the Swedish and European parliaments.
The New-York based human rights group Human Rights Watch (HRW) said Ms Estemirova had been working on "extremely sensitive" cases of human rights abuses in Chechnya.
"There is no shred of doubt that she was targeted due to her professional activity," said Tanya Lokshina, HRW Russian researcher in Moscow.
Campaign group Amnesty International said her murder was a consequence of the "impunity" allowed to persist by the Russian and Chechen authorities, and an attempt to gag civil society in the country.
BBC Moscow correspondent Rupert Wingfield-Hayes, who met Ms Estemirova in Chechnya just six weeks ago, says she was engaged in very important and dangerous work.
She was investigating hundreds of cases of alleged kidnapping, torture and extra-judicial killings by Russian government troops or militias in Chechnya.
Our correspondent says it was the government-sponsored militias that had most to fear from her work.
She is the most recent in a long line of human rights activists and lawyers to have been killed or attacked in Russia.
Our correspondent says the history of this type of case over many years is that very rarely are the killers brought to justice.