Politkovskaya, 48, known for her staunch criticism of the Kremlin and its military campaign in Chechnya, was gunned down in her apartment building in Moscow October 7.
"Investigators know the details and motive of this crime," Alexander Buxman said on Russian Radio.
But he said that although considerable progress has been made, investigators cannot yet reveal the results. "Having scrutinized the documents and materials that Politkovskaya was working on, investigators are on the track of perpetrators," he said.
The violent death of Politkovskaya prompted world leaders and international human rights activists to call on the Russian authorities to ensure that this and other high-profile murders of journalists are solved.
Politkovskaya was the author of two books on Chechnya, A Dirty War: A Russian reporter in Chechnya (2001), and Putin's Russia (2004).
The murder of Politkovskaya brings to at least 43 the number of journalists killed for their work in Russia since 1993, making the country, along with Iraq, one of the world's most dangerous for reporters.
