Anna Politkovskaya was shot dead on her doorstep
Prosecutors in the trial of three men charged over the murder of Russian journalist Anna Politkovskaya have demanded the dismissal of the judge.
Judge Yevgeny Zubov has reportedly been accused of bias and failing to follow correct procedures in the case.
He has withdrawn from the court in Moscow while the demand is considered, with a decision expected on Wednesday.
Ms Politkovskaya, a leading critic of Russia's policies in Chechnya, was shot dead outside her Moscow home in 2006.
Ms Politkovskaya's supporters believe state security agents were involved in her murder - and for that reason, they say, there will never be a fair trial at Moscow's military court.
The three men on trial are charged with involvement in the murder plot - but not with either carrying out the murder or ordering it.
The challenge to the presiding judge by the Prosecutor General's Office was the latest twist in a day of courtroom drama.
Earlier on Tuesday, the judge decided to re-open the trial to the public and lift a ban on journalists covering it.
The judge reversed his earlier decision to hold a closed-door trial
He had originally declared the trial open when the hearings opened earlier this month, but last week said it would be held behind closed doors, prompting protests from Ms Politkovskaya's family and lawyers.
Reports suggest prosecutors have questioned Judge Zubov's handling of media access to jurors and lawyers involved in the case and accused him of bias.
Earlier on Tuesday, the judge told the court he was dismissing one juror for breaking rules on not discussing the case in public.
On the same day, defence lawyer Murad Musayev told reporters that Russian prosecutors had suggested that someone abroad ordered Ms Politkovskaya's killing.
But, Mr Musayev told the court, one of the theories written in the case notes suggested that an unnamed politician, based in Russia, was behind her death.
Earlier reports suggested Mr Musayev had said the theory involving the politician inside Russia was the correct one, but he later said that this was only one of the proposals included in the case notes.
He added the indictment mentioned Ms Politkovskaya's articles as a motive for her killing.
Three men - former policeman Sergey Khadzhikurbanov and two Chechen brothers, Dzhabrail and Ibragim Makhmudov - are charged with involvement in the murder plot, but not with either carrying out the murder or ordering it.
Pavel Ryaguzov, an officer with Russia's security service, has also appeared before the court. He is charged with abuse of office and extortion.
Investigators have said Rustam Makhmudov - a third brother from the same Chechen family who is believed to have fired the fatal shot - and the person or persons who ordered Mr Politkovskaya's killing remain at large.
Some of Ms Politkovskaya's colleagues have described the trial as a "farce".
The murder of Ms Politkovskaya, who wrote for the Novaya Gazeta newspaper, shocked the international community but did not have the same impact in Russia.
Ms Politkovskaya had frequently travelled to Chechnya and the North Caucasus, where her dispatches described some of the horror of a war where most of the casualties were civilians.
She was the 13th journalist to be killed in a contract-style killing in Russia during Vladimir Putin's period as president, according to the US-based Committee to Protect Journalists.
Mr Putin - who had served the maximum two consecutive terms in office - was succeeded by Dmitry Medvedev in May.