Politkovskaya, who worked for the Moscow-based Novaya Gazeta paper, was shot dead in October 2006 in an elevator in her Moscow apartment building. Although little known in Russia, the Kremlin critic had gained a degree of international recognition for her reports of military atrocities against civilians in the troubled Caucasus republic of Chechnya.
Witness Lom-Ali Gaitukayev gave evidence on Friday in a closed court after prosecutors stated he could be in possession of sensitive information of state importance.
"In the course of giving evidence, Gaitukayev informed the court that he had found out from investigators that $2 million was paid out for the murder of Politkovskaya," the source said.
A defense lawyer earlier said that court documents indicated that an unnamed Russian politician was behind the journalist's murder.
Three men have been charged with involvement in the murder. Chechen brothers Dzhabrail and Ibragim Makhmudov have been charged with conducting surveillance on Politkovskaya, while former policeman Sergei Khadzhikurbanov has been accused of assisting them.
The eldest of the three Makhmudov brothers and the man suspected of pulling the trigger - Rustam Makhmudov - remains at large.
Gaitukayev is the Makhmudov brothers' uncle and is currently serving a 12-year jail sentence on unrelated attempted murder charges.
A former Federal Security Service (FSB) officer, Colonel Pavel Ryaguzov, has also been charged with telling the killers where Politkovskaya lived.
The trial is to resume on December 9.
