“There will be a revolution,” the vendor, Irina Lukasheva, 56, predicted. “What did our grandfathers fight for? Not for poverty or for the oligarchs sitting over there in the Kremlin.”

The protests in Khabarovsk, a city 4,000 miles east of Moscow, drew tens of thousands of people for a three-mile march through central streets for the third straight week on Saturday. Residents were rallying in support of a popular governor arrested and spirited to Moscow this month — but their remarkable outpouring of anger, which has little precedent in post-Soviet Russia, has emerged as stark testimony to the discontent that President Vladimir V. Putin faces across the country…

Khabarovsk, a city of 600,000 close to the eastern terminus of the Trans-Siberian Railway and the Chinese border, had not seen any protests of much significance since the early 1990s. That changed after July 9, when a SWAT team dragged the governor, Sergei I. Furgal, out of his car and whisked him to Moscow on 15-year-old murder accusations.

Khabarovsk social media forums erupted in indignation over an arrest that looked like a Kremlin move to eliminate a young and well-liked politician who had upset an ally of Mr. Putin in the regional election in 2018.