The murder brings the attack and death toll for human rights workers and journalists to an alarming high for the past year.

Estemirova’s was the latest in a string of murders of well-known Russian activists and journalists who have been slain after delving into human rights abuses tied to the government, especially in Chechnya. Each successive death seems to deepen the fear, anger and sense of futility among remaining activists.

In a sharp departure from Kremlin policy surrounding similar killings in past years, Russian President Dmitry Medvedev immediately deplored Estemirova’s murder, calling it an “outrage,” and demanded a high level investigation. Medvedev’s office also offered condolences to her family and said that she had been probably been killed for her human rights activities.

But many in the Russian human rights community have been dubious of Medvedev’s efforts over the past several months to cozy up to opposition groups and media. Some have suggested it is a diversionary technique to allow just such abuses to continue, Bellona’s Alexander Nikitin and Citizens’ Watch co-chair and Environmental Rights Centre Bellona board member Boris Putsytsev have suggested in interviews.  

Estemirova, who worked doggedly to document ongoing human rights abuses in war-wreaked Chechnya long after international attention had drifted away, was on her way to work when men snatched her off the street in front of her Grozny home at about 8:30, a spokesman for the prosecutors office told Bellona Web.   

She shouted for help, witnesses later told her colleagues, but the men stuffed her into a van and drove away, said the spokesman, who asked to remain unnamed as he is not authorised to speak about the case. Her body was found about nine hours later in a wooded area near Nazran, the main city of the neighboring Russian Republic of Ingushetia. She had been shot in the head and chest, the prosecutors’ spokesman said in a telephone interview.

Estemirova had been investigating human rights abuses in Chechnya for the independent Memorial group. Memorial is one of Russia’s most respected rights groups, which has been a target of government harassment, and which works to document Soviet-era abuses and those taking place more recently, especially in Chechnya.

In recent months, Estemirova had been gathering evidence of a campaign of house-burnings by government-backed militias, said Memorial.  

Estemirova, who was 50 according to Russian prosecutors, had worked in the past with the activists Anna Politkovskaya, who was shot dead in 2006.

She also worked closely with human rights lawyer Stanislav Markelov, 34, who was killed in January this year, along side Nataliya Baburova, 25, a reporter for the fiercely independent Novaya Gazeta, where Politkovskaya had worked.

At that time, Markelov had just finished a press conference protesting the early release of from prison of a Russian army colonel who had murdered an 18-year-old Chechen woman.

None of these crimes has been solved.

"We lost Anna. Now we couldn’t protect Natasha," said Alexander Cherkasov, a board member of Memorial. "She was killed for her work."

In recent years, Estemirova was one of the lone voices that still spoke out from within Chechnya to describe an underbelly of disappearances, extrajudicial killings, torture and heavy-handed autocracy that underpinned the rule of Kremlin-backed President Ramzan Kadyrov.

Estemirova had clashed repeatedly with Chechen authorities. She had contributed heavily to recent human rights reports documenting the extrajudicial punishment and burning of homes of people related to suspected anti-Kadyrov rebels, according to reports by Russian media and western human rights groups.

She had also contributed to a report released Wednesday that called for Russian officials, including Prime Minister Vladimir Putin, to be held accountable for human rights crimes.

"There’s an atmosphere of impunity," Estemirova said in an interview last year with the Los Angeles Times.

"We have a list of more than 4,000 people still missing and there are many cases in which we have hard evidence against people who kidnapped them, we even have their names and ranks, but it’s impossible to initiate an investigation," she said.

Earlier this month, she had publicised the case of a man who was shot to death in the streets of a Chechen village, without trial or investigation, for alleged ties to the rebels, the Los Angeles Times reported.

"The Chechen authorities immediately made it known . . . that Memorial should not air the household garbage in public like that," Cherkasov said.

In 2007 she was awarded the inaugural Anna Politkovskaya Prize, and had also received awards from the Swedish and European parliaments, Memorial said.

Memorial said it believes that government security services of some nature must be involved in her killing.

The New-York based human rights group Human Rights Watch (HRW) said 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," Tanya Lokshina, HRW’s Russian researcher in Moscow, said in a telephone interview.

Campaign group Amnesty International said in  statement that Estemirova’s murder was a consequence of the impunity that has been allowed to persist by the Russian authorities as an attempt to gag civil society in the country.

In April, Lev Ponomaryov, 67, leader of the organization For Human Rights and a founding member of Memorial was beaten outside his home.

In February, 72-year-old opposition newspaper editor Yury Grachev was beaten in the Moscow suburb of Solnechonogorsk by unknown assailants. Police investigating the case dismissed the attack on the editor of the investigative newspaper that exposed numerous acts of official corruption as self-inflicted injuries.

In December, at least one unidentified assailant shot in the head and wounded Shafig Amrakhov, 51, editor of the Murmansk-based online regional news agency RIA. He died after a week in the hospital. Earlier the same month, two unidentified assailants attacked and beat Zhanna Akbasheva, a local correspondent for the independent news agency Regnum, in the North Caucasus Republic  of Karachai-Cherkessiya.

In November 2008 Mikhail Beketov, editor of the authority-rankling Khimskaya Pravda newspaper, was beaten nearly to death in the Moscow suburb of Khimki. His paper wrote exposés on corruption and campaigned on environmental issues.

Beketov’s supporters say he made enemies by campaigning against a plan to build a toll highway between Moscow and St Petersburg through a forest on the outskirts of Khimki.

These crimes, likewise, remain unsolved.