Russia’s investigation into the murder of the journalist Anna Politkovskaya appeared to be close to collapse yesterday only a week after ten arrests were announced in a blaze of publicity.

It emerged that the chief investigator in the inquiry had been demoted, while the Prosecutor-General Yuri Chaika’s case against several of the suspects had already fallen apart.

Two of the men have been released because of lack of evidence and a third has been found to have a watertight alibi - he was serving a prison sentence at the time Ms Politkovskaya was murdered in October.

A Moscow court has also overturned the arrest of an officer in the Federal Security Service (FSB), the successor to the KGB, who was named as a suspect hours after Mr Chaika announced the breakthrough in the case.

Staff at Novaya Gazeta, the newspaper where Ms Politkovskaya worked, expressed “deep disappointment and bewilderment” at the decision to replace Pyotr Garibyan, the lead investigator, with a more senior official.

The newspaper, which has been working with the inquiry, has praised Mr Garibyan’s work. Dmitry Muratov, the editor-in-chief, accused Kremlin officials linked to the military and security services, known as the siloviki, of interfering with the inquiry.

“The siloviki are achieving what they set out to achieve. They wanted to ruin the case, and now they will remove Garibyan and finish that process,” Mr Muratov told Ekho Moskvy radio.

Ms Politkovskaya’s son, Ilya, said he was also disappointed. The Prosecutor-General’s Office insisted that it had simply expanded the inquiry team and put the head of the investigations department in overall command.

The developments cast a shadow over the inquiry, which appeared to be making progress in solving the murder of President Putin’s most outspoken critic. Ms Politkovskaya was shot dead in the lobby of her apartment building on October 7, the President’s 54th birthday.

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