Tens of thousands of people have taken to the streets in Russia's Far East in a rare show of defiance against the Kremlin as they protested the arrest of a popular governor.

Axar.az reports citing foreign media that the huge rallies in the city of Khabarovsk on the border with China present a growing headache for the Kremlin, observers say, and come after President Vladimir Putin this month oversaw a controversial vote that allows him to extend his hold on power until 2036.

Protesters carried placards reading "Freedom for Furgal!" and cried out "As long as we are united, we are invincible", as passing cars honked horns in support.

Furgal's unexpected victory in the gubernatorial election reflected growing public frustration with President Putin's policies and marked a big setback for the main Kremlin party, United Russia.

Many of the protesters say the charges are politically motivated and question why investigators waited so long to accuse a public official who should have undergone background checks.