MOSCOW (AFP) - A Moscow court on Wednesday ruled against jailing leading opposition politician Alexei Navalny after the prison authorities asked for his suspended sentence to be turned into a custodial term.

A nail-biting hearing in southern Moscow saw Navalny, a charismatic protest leader and one of President Vladimir Putin's biggest critics, arrive at the courtroom with a large bag of his belongings packed to take to a penal colony.

The prison service had asked the judge to convert a suspended five-year term Navalny received in 2013 into jail time over his alleged non-compliance with the conditions of his sentence.

Navalny received the suspended sentence after a highly controversial trial over his purported embezzlement from a timber firm in the northern Kirov region.

Since then, the 38-year-old lawyer, who shot to prominence with his online anti-corruption campaigns and rousing rhetoric at protests, has received a second fraud conviction and faces a string of probes against him and his associates.

His supporters charge that the decisions on his cases originate in the Kremlin rather than in court.

Navalny jested after Wednesday's hearing that everyone was "tired of the endless questions about whether Navalny will be jailed this time or not".

"We won't give up. We understand there are threats and pressure, but we'll continue our work," he said.

Navalny ran for Moscow mayor in 2013 on the ticket of the party of Boris Nemtsov, the former deputy prime minister who was assassinated in February.

Nemtsov finished second in the mayoral race.

He announced this year that his own Party of Progress was interested in participating in 2016 legislative elections - only for the justice ministry to cancel the party's registration several days later.