MELEKHOVO, Aug 5 (CNA) - Jailed Russian opposition politician Alexei Navalny had an extra 19 years added to his jail term on Friday (Aug 4) in a criminal case which he and his supporters said was trumped up to keep him behind bars and out of politics for even longer.

Navalny, 47, President Vladimir Putin's fiercest domestic critic, is already serving sentences totalling 11 and a half years on fraud and other charges that he says are also bogus. His political movement has been outlawed and declared "extremist".

A court at the IK-6 penal colony in Melekhovo, about 235km east of Moscow where he is serving his sentences, was trying him on Friday on six separate criminal charges, including inciting and financing extremist activity and creating an extremist organisation.

The audio feed from the court was so poor that it was practically impossible to make out what the judge was saying.

Navalny's team said the judge had added 19 years to his sentences as a result of the new charges. State prosecutors had asked the court to hand him another 20 years in a penal colony.

Dressed in his dark prison uniform and flanked by his lawyers, Navalny smiled at times as he listened to the judge.

In a message posted on social media a day earlier Navalny had predicted he would get a long jail term, but had said it didn't really matter because he was also threatened with separate terrorism charges that could bring another decade.

Navalny had said the purpose of giving him extra jail time was to frighten Russians, but had urged them not to let that happen and to think hard about how best to resist what he called the "villains and thieves in the Kremlin".

The charges relate to his role in his now defunct movement inside Russia, which the authorities said had been trying to foment a revolution by seeking to destabilise the socio-political situation.

German Foreign Minister Annalena Baerbock condemned the ruling. "Russia's arbitrary justice system imprisoning Alexei Navalny for another 19 years is pure injustice," she wrote on social media.

"Putin fears nothing more than standing up against war and corruption and for democracy - even from a prison cell. He will not silence critical voices with this."