"The authorities are incapable of solving such crimes," said Mikhail Kasyanov, a former prime minister and now a leader of the opposition. "Even the most honest investigator cannot solve the crime because the government won't let him."
Politkovskaya, an internationally known journalist, was a harsh critic of the Kremlin and exposed widespread human-rights abuses and corruption in Chechnya. Prosecutors have said little about who might have ordered the contract-style killing of her on Oct. 7, 2006, while the suspected gunman is believed to be hiding abroad. Three men accused of playing minor roles in the killing remain under investigation.
Since Politkovskaya's death, at least seven journalists and human rights activists have been killed in Russia, including one who wrote for the same newspaper, Novaya Gazeta.
"There is a political will not to solve the murders," Dmitry Muratov, the newspaper's editor, told the crowd that had gathered in a Moscow park.
U.S. Secretary of State Hillary Rodham Clinton released a statement late Wednesday, saying: "The failure to bring to justice the killers of these journalists undermines efforts to strengthen the rule of law, improve government accountability, and combat corruption."
Some of Russia's most prominent human rights activists and opposition leaders took part in the Moscow rally, which began with a minute of silence at 4:03 p.m. (1203 GMT), the time Politkovskaya was shot in her apartment building three years ago.
The demonstration, in typical fashion, was heavily policed. City Hall had forbidden a gathering of more than 350 people.
Many held photographs of Politkovskaya _ who also wrote books critical of the Kremlin and Prime Minister Vladimir Putin _ and bouquets of roses, which they later placed outside her apartment building in central Moscow. Dozens more joined them in paying their respects to the slain journalist.
Flowers were taped to the building's wall and placed against a large color poster of Politkovskaya. A smaller poster read: "The smart, honest and brave cannot survive in Russia."
A policeman jotted down the slogans on a scrap of paper.
Neither President Dmitry Medvedev nor Putin, who was president when Politkovskaya was killed, commented about her death Wednesday.
Medvedev came to power 18 months ago on promises of cementing the rule of law, but critics are still awaiting action.
Former Prime Minister Kasyanov said Russia had seen "a significant deterioration" over that time.
Putin, meanwhile, celebrated his 57th birthday Wednesday and marked the occasion by meeting with several writers.
Putin made his first public remarks on Politkovskaya's death days after it occurred, saying it did more to harm to Russia than her articles did.
A Russian journalist who had gone into hiding, meanwhile, made a surprise appearance at Wednesday's rally. Alexander Podrabinek has been followed by Kremlin-friendly youth groups since writing an article several weeks ago that criticized Soviet war veterans.
Podrabinek made a hasty exit after addressing Politkovskaya's supporters about censorship in Russia.
Memorial events for Politvkoskaya also were planned in London and Paris.