A Moscow judge on Saturday upheld a ruling to jail top Kremlin critic Alexei Navalny, as he lost two court cases in one day and was headed for more than two years in a penal colony.

Another court later Saturday convicted President Vladimir Putin's most prominent opponent on defamation charges -- part of a slew of cases he has faced since returning from Germany last month after a poison attack he blames on the Kremlin.

In the first hearing on Saturday, Judge Dmitry Balashov dismissed Navalny's appeal of a decision to imprison him for violating the terms of a suspended sentence on embezzlement charges he says were politically motivated.

Navalny, 44, was ordered on February 2 to serve two years and eight months in a penal colony for breaching his parole terms while he was recovering in Germany.

The anti-corruption campaigner appeared in court inside a glass cage for defendants, wearing a plaid shirt, smiling and flashing the V for victory symbol.

In a closing address that often broke from his usual sarcastic tone, Navalny referenced the Bible and said he had no doubts about his decision to return to Russia.

"The Bible says: 'Blessed are those who hunger for righteousness, for they will be satisfied,'" he told the court.

"I have no regrets that I am back."

He also quoted from a character in the Harry Potter books, saying it was "important not to feel alone" because that was what the series' villain Voldemort wanted.

He described the legal process to jail him "absurd" and called on Russians to take action to make the country a better place.

"Russia should be not only free but also happy," Navalny said. Prosecutors said Navalny had acted as if he was above the law and had "an exclusive right to do as he pleases".

The judge decided to count six weeks Navalny was under house arrest as part of the time served, so he will now be imprisoned for just over two-and-a-half years.

Hours later another judge convicted Navalny of defamation for calling a World War II veteran a "traitor" for appearing in a pro-Kremlin video. Judge Vera Akimova ordered him to pay a fine of 850,000 rubles ($11,500/9,500 euros).

Before the judge began reading the verdict Navalny made jokes from inside his glass box. "Why are you so sad?" he told reporters, adding he was trying to make ice cream in jail and had already made pickled cucumbers.

One of his two lawyers, Olga Mikhailova, said Navalny was not expected to be sent off to a penal colony before his defence team received a copy of the verdict. The 94-year-old veteran appeared in a video that Navalny derided for promoting constitutional reforms, passed last year, that allow Putin to stay in power until 2036.

Navalny accused Russian authorities of using the veteran as a "puppet" to try to discredit him. "One day of this trial costs much more than the veteran got in the last four years from the very state that dares to claim it cares about veterans," he said. Supporters of the opposition politician say the cases are a pretext to silence his corruption exposes and quash his political ambitions.