The Supreme Court in Russia's Bashkortostan region increased the prison sentence for a former staffer of the late opposition leader Alexei Navalny on Tuesday to 9-1/2 years from 7-1/2, Navalny's team said on Telegram.

Liliya Chanysheva, the former head of Navalny's office in the central region, and her former colleague Rustem Mulyukov were the first Navalny staffers to be convicted of national security charges after his organisation was deemed "extremist" by the authorities in 2021.

Chanysheva was handed a seven-and-a-half-year sentence last year for participating in Navalny's organisation, while Mulyukov received two-and-a-half years for similar charges.

A Russian prosecutor asked last month for Chanysheva's sentence to be increased to 10 years because she had "provoked and incited Ufa residents" to protest in the streets, referring to Bashkortostan's capital.

Navalny's team said Russian authorities were exacting "vile revenge" against Chanysheva for what they called her "struggle against lying, looting of the country and poverty."

Navalny, President Vladimir Putin's fiercest critic inside Russia, died in an Arctic prison camp at age 47 on Feb. 16, sparking accusations from supporters that he had been murdered. The Kremlin has denied any state involvement in his death. REUTERS