World activists accused the Russian state of sabotaging a probe into the abduction and murder three years ago Sunday of an award-winning campaigner for those struggling in the crisis-torn Caucasus.

Natalya Estemirova was bundled into a car moments after stepping out of her home in the Chechen capital Grozny on the morning of July 15. Her blood-stained body was dumped near a highway in next-door Ingushetia only a few hours later.

The 50-year-old Memorial rights group worker had been looking into the alleged public execution of a man by Chechen police at the time of her killing and was a public opponent of strongman Ramzan Kadyrov's Kremlin-backed rule.

"We have seen absolutely no progress in the search for the real culprits," Memorial chief Oleg Orlov told Moscow Echo radio.

"The investigation team is coming under two forms of sabotage," he noted.

"There is sabotage from the heads of the Committee. And then there is sabotage from (Chechen officials) on the ground who are supposed to be helping the investigation."

Amnesty International for its part said it had been forced to conclude that the Russian authorities never actually intended to find those responsible for the murder.

The absence of any progress "can only be explained by a lack of political will to end impunity for such crimes," the global rights group's regional director John Dalhuisen said in a statement.

"We have to conclude that the Russian authorities gave hollow promises that they never meant to fulfil," the Amnesty International representative said.

Estemirova's death and 2006 Moscow shooting of Chechen campaigners and Novaya Gazeta newspaper report Anna Politkoskaya have embodied fears about links between the Chechen authorities and violent organised crime.

Both shootings -- raised repeatedly during foreign state visits by President Vladimir Putin and his predecessor Dmitry Medvedev -- appear to have been well-planned and involved victims who were regarded as public enemies by Kadyrov.

The authoritarian ruler of the once-separatist and war-devastated republic denies any link to either attack.

A Kremlin rights panel submitted a report to Medvedev on the death's second anniversary last year accusing the powerful Federal Security Service -- once headed by ex-KGB agent Putin -- of itself torpedoing the investigation.

Medvedev never responded to the 2011 report and in May ceded his Kremlin seat to Putin in favour of the prime minister's post.

Rights groups blamed the state's inaction for sustaining a sense of impunity among corrupt and criminal local officials that has led to the disappearance or murder of at least four other campaigners in the past three years.

"With Estemirova's murder, the situation for human rights workers in Chechnya and other parts of the North Caucasus deteriorated sharply," said Tatyana Lokshina of Human Rights Watch in Moscow.

Lokshina said those still missing included a local staffer of the Danish Refugee Council who vanished in Grozny in October 2009.

Putin, since his return to the Kremlin for a third term, has been waging a new crackdown on non-governmental organisations such as Memorial that includes a bill branding them "foreign agents" for accepting US and European funding.

The campaign extends a history of acrimonious relations with rights movements that carries over to periodic diplomatic tensions with the West.

Many at Memorial particularly remember Putin for dismissing the work of Navaya Gazeta reporter Politkovskaya as "extremely insignificant" shortly after her death -- comments apparently aimed at proving the state's innocence in her case.

AFP Photo/Oxana Onipko