By Aydar Buribayev and Amie Ferris-Rotman
MOSCOW (Reuters) - The abduction and murder of a prominent human rights activist from Chechnya sparked international outrage on Thursday and her grieving supporters asked "Who is next?."
Friends carried Natalia Estemirova's body from neighbouring Ingushetia, where she was dumped in woodland after she was abducted as she left home, and buried her in Chechnya.
German Chancellor Angela Merkel urged Russia to clarify the circumstances surrounding her killing.
"I expressed my shock at the death," Merkel said after meeting Russian President Dimitry Medvedev in Germany.
Medvedev called it "a very sad event" and said he was determined to find and punish Estemirova's killers.
His remarks contrasted to those of Prime Minister Vladimir Putin, who when president in 2006 was dismissive of slain Russian journalist Anna Politkovskaya, saying she had "minimal influence" on Russian society.
Politkovskaya was gunned down in her Moscow apartment building in 2006. Nobody has been convicted of her murder.
The human rights organisation she worked for, Memorial, and Helsinki Group, Russia's oldest NGO, blamed Chechnya's Kremlin-backed president for Estemirova's killing.
Amnesty International said it stemmed from a culture of impunity both within Chechnya and in Russia as a whole. The United States called it an "outrageous crime."
A close friend of Politkovskaya, Estemirova, aged about 50, and who leaves a 15-year-old daughter, worked for Memorial in the Chechen capital Grozny and documented abuses by law enforcement agencies.
Her abduction in Chechnya on Wednesday and killing was the latest of a series of deaths of establishment critics which have led to questions about Medvedev's pledges to uphold the law.
Russia's Interior Minister Rashid Nurgaliyev told reporters in Munich the government was pursuing several scenarios, while prosecutor General Yury Chaika was shown on Russian television saying he would take personal control of the case.
Memorial's chairman Oleg Orlov blamed Chechen President Ramzan Kadyrov, an ex-rebel turned Kremlin loyalist.
"I know, I am sure of it, who is guilty for the murder of Natalia ... His name is Ramzan Kadyrov," he said in a statement.
"Ramzan already threatened Natalia, insulted her, considered her a personal enemy."
Kadyrov's spokesman said her killers would be punished.
"Estemirova defended human rights. She couldn't possibly have had enemies amongst clear-thinking people," he said. "Those who took her life do not deserve to be called people. They deserve no mercy and they should be punished as the cruellest of criminals."
BURIED IN HER NATIVE CHECHNYA
Friends took Estemirova's body, wrapped in a green and floral blanket, out of a yellow van in her native village of Ishkoi-Yurt in Chechnya.
Dozens of women sobbed under the blazing sunshine as men gave condolences to her family. She was buried in a cemetery in the small town of Koshkeldy, a witness said.
In front of her office in Grozny, a black-clad mourner held up the sign "Who is next?," TV showed.
In Moscow, around 100 people stood silently near a central square, some holding photos of Estemirova and Politkovskaya.
"I wish to believe in the sincerity of his words ... I don't have faith that we will see the right people in the dock," said supporter Natalia Rostova of Medvedev's promise.
IHS Global Insight said the authorities could be responsible.
"There are plausible signs that the perpetrators either belonged to the security forces or had false identifications, as they managed to cross the tightly guarded border between Chechnya and Ingushetia," analyst Natalia Leshchenko said.
Her body was found with two wounds to the head and the Ingush Interior Ministry said she had been murdered on Wednesday morning. Rights groups said she had been shot.
Rights groups said Estemirova -- the inaugural recipient in 2007 of the Anna Politkovskaya Award given by the charity Reach All Women in War -- was snatched as she left home, and cried out she was being kidnapped as she was forced into a vehicle and driven away.
Separatists in mainly Muslim Chechnya fought two wars against Moscow in the 1990s. It still faces a simmering Islamist insurgency along with Ingushetia and Dagestan.
Human rights groups have repeatedly accused the authorities in Chechnya of serious abuses including house burning, extra-judicial killings, torture and illegal punishment.
(Additional reporting by David Alexander in Washington and Oleg Shchedrov in Munich; Editing by Alison Williams)