Estemirova was abducted in the capital of Russia's volatile North Caucasus region of Chechnya, Grozny, on July 15, 2009. Her bullet-riddled body was found hours later in neighboring Ingushetia.

The Memorial human rights center, where Estemirova worked until her abduction and death, and 11 Russian and international human rights organizations issued a joint statement on July 14 calling on Russian authorities to "at last carry out its obligations and conduct a thorough, unbiased, and effective investigation into the killing, bring individuals responsible for the crime to justice, and stop impunity for violation of human rights in Chechnya."

Human Rights Watch and Amnesty Internationalissued an English-language version of the statement on July 15.

“We are still waiting for the Russian government to carry out an effective investigation into the murder of our friend and colleague, Natalya Estemirova,” said Tanya Lokshina, associate Europe and Central Asia director at Human Rights Watch. “The government’s inaction in this heinous crime is a black stain that perpetuates human rights abuses in Chechnya.”

“The courage and selflessness of Natalya Estemirova, who investigated abductions, extrajudicial executions, and other grave violations of human rights in Chechnya was unparalleled,"said Marie Struthers , Amnesty International’s director for Eastern Europe and Central Asia.

"There is no doubt that she paid with her life for this fearless work. Ten years on, the Russian authorities have manifestly failed to find the perpetrators of this crime and those who ordered it.”

Also, on July 15, human rights activists Aleksandr Cherkasov and Svetlana Gannushkina and journalist Yelena Milashina were detained by police on Moscow's Red Square after they held Estemirova's portrait and posters reading, "Human rights activist Natalya Estemirova was killed 10 years ago," "Those who ordered and conducted the killing have not been found," and "Why is that, Mr. President?"

Estemirova, who led Memorial's office in Chechnya, was renowned for her writing and activism on human rights abuses in Chechnya and nearby regions in the North Caucasus.

Ramzan Kadyrov, the Kremlin-installed leader of Chechnya, has been accused of gross human rights abuses for many years, including abductions, torture, and killings.

Rights activists say that Kadyrov rules through repressive means and has created a climate of impunity for security forces in Chechnya.

Kremlin critics say Russian President Vladimir Putin turns a blind eye to Kadyrov's frequent violations of the Russian Constitution because he relies on the former rebel commander to control separatist sentiments and violence in the region.

Chechnya was the site of two devastating post-Soviet wars and an Islamist insurgency that spread to other mostly Muslim regions in the North Caucasus.

Estemirova's 25-year-old daughter, Lana, who traveled to Moscow from London, where she has been residing for years, told Current Time TV that she thinks that more than one person is responsible for her mother's death.

"All are guilty [for my mother's death] -- Putin, Kadyrov, and the entire system they have built in the last 20 years," she told Current Time, the Russian-language network led by RFE/RL in cooperation with VOA.

"The system where you can't tell the truth without facing consequences, the system that does not allow criticizing the authorities' actions or inaction -- the whole system is guilty."

She added that Natalya Estemirova fought against that system and so are "hundreds of human rights activists and journalists and lawyers."

Lana Estemirova also said that she agrees with Memorial's official position that her mother's abduction and killing was linked to her investigations into the kidnappings of ordinary Chechens by the region's Kurchaloi district police.

With reporting by Current Time TV