'The militias had much to fear from her,' says the BBC's Rupert Wingfield-Hayes
A prominent Russian human rights activist, Natalia Estemirova, has been found dead in the North Caucasus.
She was bundled into a van and abducted as she left her home in Chechnya on Wednesday morning, a colleague said. Her body was found in Ingushetia.
The Russian President Dmitry Medvedev expressed "outrage" at the murder, and ordered a top-level investigation.
Ms Estemirova had been investigating human rights abuses in Chechnya for the independent Memorial group.
Memorial is one of Russia's best known rights groups, working to document Soviet-era abuses and those taking place more recently, especially in Chechnya.
In recent months, she had been gathering evidence of a campaign of house-burnings by government-backed militias.
Ms Estemirova, who was 50 according to Russian prosecutors, had worked in the past with the activists Anna Politkovskaya, who was shot dead in 2006, and Stanislav Markelov, who was killed in January this year.
There is no shred of doubt that she was targeted due to her professional activity
In 2007 she was awarded the inaugural Anna Politkovskaya Prize, and had also received awards from the Swedish and European parliaments, Memorial said.
In a statement the group said she "was forcefully taken from her house into a car and shouted that she was being kidnapped" at about 0830 local time (0430 GMT).
Her body was found in woodland near Nazran, the main city in neighbouring Ingushetia, about nine hours later. She had bullet wounds to the head and chest.
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's Russian researcher in Moscow.
Campaign group Amnesty International said her murder was a consequence of the impunity that has been allowed to persist by the Russian and Chechen authorities and an attempt to gag civil society in the country.
In a statement, Irene Khan, the organisation's head, described her as "a courageous and inspiring woman".
"Human rights violations in Russia, and especially in the North Caucasus, can no longer be ignored. And those who stand up for human rights need protection," she said.
"The terrible tragedy of the killing of Natalia Estemirova is a crime that should be denounced by the authorities and every effort must be made to bring those responsible to justice."
Ms Estemirova was engaged in very important and dangerous work, says the BBC's Rupert Wingfield-Hayes in Moscow, investigating hundreds of cases of alleged kidnapping, torture and extra-judicial killings by Russian government troops or militias in Chechnya.
Memorial says it believes that government security services of some nature must be involved in her killing.
Our correspondent says no evidence of that has emerged so far, but that 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. The history of these sorts of cases over many years is that very rarely are their killers ever brought to justice, our correspondent says.
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