Russia has arrested a former senior police officer suspected of organising the 2006 murder of anti-Kremlin reporter Anna Politkovskaya in exchange for cash, investigators said on Wednesday.
The announcement marks a major development in the long-running case that has failed to secure any convictions after half a decade. The investigators said they also had information on the supposed mastermind of the killing.
Retired police lieutenant colonel Dmitry Pavlyuchenkov is suspected of organising the criminal group that carried out the murder as well as obtaining the murder weapon, said the spokesman for the Investigative Committee Vladimir Markin.
"According to the investigation, Pavlyuchenkov received the order to organise the killing of Anna Politkovskaya from an unknown individual in exchange for a monetary reward and gave his agreement," he said in a statement carried by Russian news agencies.
The arrest, which was made after questioning on Tuesday, was first announced by the editor-in-chief of Politkovskaya's Novaya Gazeta newspaper Dmitry Muratov late on Tuesday.
A trenchant critic of the Kremlin, Politkovskaya had won international prizes for her reports accusing Prime Minister Vladimir Putin of using the Chechen conflict to strangle democracy while he was president.
Her killing sparked international outrage and underlined the lack of security faced by reporters in Russia who dare to challenge the authorities.
Politkovskaya was shot dead in October 2006 in her apartment block in Moscow and failure of the investigation to secure any convictions has been widely ridiculed in Russia and abroad.
In another major possible lead, Markin also said investigators had information on the supposed mastermind of the killing, who has never been identified let alone arrested.
"For the moment we think it premature to make this information public," he added.
Two Chechen brothers, Dzhabrail and Ibragim Makhmudov, and former police officer Sergei Khadzhikurbanov were tried for suspected involvement in the killing but were acquitted on a lack of evidence in 2009.
This verdict was then annulled by the supreme court and a new investigation reopened with the same suspects. The authorities in June arrested a third Makhmudov brother, Rustam, on suspicion of carrying out the murder.
Markin said that Pavlyuchenkov is suspected of hiring the Makhmudov brothers to carry out the crime and also obtaining the pistol allegedly used by Rustam Makhmudov.
"Pavlyuchenkov promised the Makhmudov brothers a monetary reward for carrying out the order," said Markin.
According to Markin, Pavlyuchenkov told the brothers where Politkovskaya lived in central Moscow as well as the make of car that she drove. The group was then able to trail her to confirm her routine before the murder was carried out.
Pavlyuchenkov was a witness in the trial against the three suspects where, according to the Novaya Gazeta, he sought to present himself as a valuable source and gave information that was made-up.
Veteran Russian rights activist Lyudmila Alexeyeva applauded the apparent renewal of interest in the case but expressed doubt if the investigators would in the end find those who were truly behind the killing.
"I am happy that they have returned to the Politkovskaya case, that they have taken it away from the dead end. But there are doubts," she told AFP.
Putin famously said in the days after her murder that the killing was "an unacceptable crime that cannot go unpunished" but also described her capability to influence politics in Russia as "insignificant".