A year after a human rights worker, Natalia Estemirova, was abducted outside her home in Chechnya and found dead beside a highway, the Russian president, Dmitry A. Medvedev, said the authorities had identified her killer and were searching for the person who ordered her murder. Medvedev did not offer details, but a senior investigator on the case confirmed that Akhazhur Bashayev, an anti-government militant, was suspected of killing Estemirova. Estemirova's colleagues and relatives rejected this explanation on Thursday, urging authorities to investigate the theory they have put forward -- that she was killed by forces linked to the Chechen government that were unhappy with her inquiries into police abuses. 'We're asking Mr. Medvedev openly: What has been done to look into the theory of possible official involvement?' said Tanya Lokshina, deputy director of the Moscow office of Human Rights Watch. 'We are asking the Russian government for concrete information.' Much of Estemirova's work focused on kidnapping and other abuses she believed had been carried out under the authority of the Chechen president, Ramzan A. Kadyrov, who has enjoyed unwavering support from the Kremlin. Beginning hours after her disappearance, her colleagues said they believed that Kadyrov, or forces linked to him, were responsible. But Medvedev immediately dismissed theories that implicated Kadyrov, calling them 'primitive,' and Kadyrov angrily denied any role in Estemirova's death. The official investigation has evidently gone in another direction. Igor Sobol, head of investigations at the investigative committee for the southern federal district prosecutor's office, said the killer was believed to be Bashayev. Bashayev was reported killed in a counterterrorism operation in November, but Sobol said his death had not been officially confirmed. According to the newspaper Novaya Gazeta, which obtained and published an internal investigative report from the case last week, the police identified Bashayev in January, after they found the murder weapon lying next to an identification document with his picture attached to it. Local people told the police that Estemirova had been in Bashayev's village in April, gathering information about the militant group, and files about the insurgent group were found on her laptop, the newspaper reported. Roman Karpinsky, a lawyer representing Estemirova's sister, Svetlana, said he was 'very skeptical' that Bashayev was the culprit. 'It seems to me there are more convincing theories, which demand meticulous investigation,' he said, noting that Estemirova's closest associates were convinced that she was killed because she was looking into a public execution carried out last July 7 by the local police. Her inquiries, he said, 'aroused dissatisfaction among Chechen officials.' 'We consider that this theory should be, at minimum, checked out,' he said. Estemirova's colleagues were also sharply skeptical on Thursday. Aleksandr Cherkasov, a researcher at Memorial, the human rights group where she worked, said her colleagues in Grozny, the capital of Chechnya, were certain she had never traveled to Salazhi, Bashayev's village. He also said she had never published any work about Bashayev or his insurgent group. To quiet the furor around Estemirova's death, Cherkasov said, 'a dead rebel was appointed the murderer.' 'It's very convenient because,' he said, 'a) because the case will be considered to have been investigated, and b) because the comrade did not live long enough to go to court.' He added that the evidence implicating Bashayev was so forthcoming that 'it's almost as if he turned himself in.' Medvedev, who was meeting with the German chancellor, Angela Merkel, in Yekaterinburg on Thursday, is under international pressure to solve Estemirova's murder. Amnesty International said the inquiry's slow pace 'raises concerns that there is no political will to identify the perpetrators,' and the Council of Europe's human rights commissioner, Thomas Hammarberg, called the lack of any arrest 'unacceptable.' Medvedev defended Russia's efforts, saying it was 'false to say that there is no investigation.' 'We have established and positively identified the perpetrator of this murder -- the killer,' he said. 'Now we have undertaken an investigation to find not only the killer, who is already the target of a manhunt, but also the person who ordered this grave crime.' Sobol, the investigator, said the police had considered 'all possible theories' of Estemirova's murder, 'including the theory related to the person who ordered it.' But he said the investigation was continuing, so he could not speak further about it. 