Jailed Kremlin critic Alexei Navalny has launched a fresh attack Tuesday against President Vladimir Putin, telling a Moscow court that Russia’s invasion of Ukraine is a "stupid war" which the strongman started. 

Navalny made the comment as Russia’s ongoing war of Ukraine has reached the three-month mark. 

"This is a stupid war which your Putin started," Navalny said after unsuccessfully appealing his nine-year sentence for fraud and contempt of court charges, which he denies, according to Reuters. "This war was built on lies." 

Kremlin critic Navalny criticizes Putin during Moscow court appearance

Russian opposition leader Alexei Navalny is seen on a screen via a video link from the IK-2 corrective penal colony in Pokrov during a court hearing to consider an appeal against his prison sentence in Moscow, Russia, on Tuesday, May 24. (REUTERS/Evgenia Novozhenina)

"One madman has got his claws into Ukraine and I do not know what he wants to do with it -- this crazy thief," Navalny continued. 

TOP RUSSIA UN DIPLOMAT QUITS OVER UKRAINE WAR, SLAMS PUTIN 

In the early days of the war, Navalny urged Russians to stage daily protests and called Putin an "obviously insane czar" for his invasion of Ukraine that began on Feb. 24. 

Alexei Navalny used a court appearance Tuesday to criticize Russian President Vladimir Putin over his invasion of Ukraine.

Alexei Navalny used a court appearance Tuesday to criticize Russian President Vladimir Putin over his invasion of Ukraine.

In a long series of tweets posted at the time by his spokesman, Navalny told his people to avoid turning into a "nation of frightened silent people" and instead "fight for peace." 

Now on Tuesday he warned the Russian court that "you will all suffer historic defeat." 

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Russian opposition leader Alexei Navalny Moscow march

Russian opposition leader Alexei Navalny takes part in a march at Strastnoy Boulevard in memory of Russian politician and opposition leader Boris Nemtsov in Moscow, Russia on Feb. 24, 2019. (Sefa Karacan/Anadolu Agency/Getty Images)

"What do you want to achieve -- do you want short-term control, to fight with future generations, to fight for the future of Russia?" Navalny reportedly told the court Tuesday as a judge repeatedly interrupted him.  

"Your time will pass," Reuters also quoted Navalny as saying. "When you will all be burning in hell, your grandfathers will be adding wood to your fires."