MOSCOW — An unlikely protest movement has become the first major challenge to Russian President Vladimir Putin after he secured his political future in a contentious vote this month — and it may spell more trouble in the days ahead.

Residents of Khabarovsk, a large city near Russia’s border with China, have been up in arms for days protesting the arrest of their governor on 15-year-old murder charges.

The governor whom the protests are defending, Sergei Furgal, is himself no hero.

As a member of one of Russia’s two Kremlin-sanctioned opposition parties — the Liberal-Democratic Party, a nationalist outfit that is neither liberal nor democratic — Furgal has spent most of his two years as governor more or less toeing Moscow’s party line in the far east, not causing any trouble. He was, essentially, a loyalist.

But Furgal committed an unforgivable sin against the regime: In the 2018 gubernatorial elections, he rebuffed Kremlin calls to fold and allow the favored United Russia party candidate to win. He then went on to legitimately win a popular contest. Many residents of Khabarovsk say they see his arrest last week as punishment.

But more important, they say they see the arrest as a usurpation of local political will. Furgal managed to do a few genuinely popular things in his two years in office, a 25-year-old office worker said on condition of anonymity, fearing reprisal for taking part in the protests.

“This was a governor that was honestly elected by the people, which is unusual in Russia,” she said. “He was in power for just two years, but he did a lot for the people: He fixed the region’s budget, repaired the roads, gave schoolchildren free breakfast. And he was removed on unfair charges. There are so many injustices in the far east, and this was the last straw.”

And so, on Saturday, 30,000 people took to the streets of Khabarovsk to demand his release. Protests have continued every day since. Demonstrators have held banners saying “Free Sergei Furgal,” while others have called on Putin to resign.

“How can a person who has been in politics for so many years hide murders for 15 years? At all stages, civil servants are checked, and it is impossible to hide such a thing,” the office worker said, reflecting a sentiment shared by other protesters across social media. “Either he didn’t do it, or he did and the Kremlin covered for him for 15 years while it was beneficial for them.”

The Kremlin appears to have been at least slightly taken aback by the public response. Putin has yet to publicly comment, and state television has avoided coverage.

Although Furgal, 50, has been under arrest in Moscow since July 9, the Kremlin hasn’t yet formally removed him from his post. But a Kremlin envoy dispatched to meet with local government officials has doubled down on the charges, claiming that the security services wouldn’t have made a move were they not 100 percent confident.

Furgal is charged in the deaths of several businessmen in 2004 and 2005, when he was a businessman himself with interests in importing consumer goods, timber and metals before he got into politics. He denies the charges. Before becoming governor in 2018, he spent a decade in the State Duma, Russia’s lower house of Parliament.

The reaction to Furgal’s arrest reveals local tensions between Moscow, as a political center, and the regions it presides over in an increasingly centralized manner. But the arrest is also part of a broader crackdown on opposition voices of all types — from the most radical to the most conformist — that in many ways feels like a settling of old scores.

The Kremlin declared victory July 1 in a referendum on constitutional amendments that, among other things, reset Putin’s term limits — allowing him to rule Russia until 2036 if he chooses. Since then, there has been almost daily news of repressive actions.

The Central Election Commission reported that 78 percent of voters supported the changes, with a record 68 percent turnout. Opposition leaders such as Alexei Navalny have slammed the referendum as the most fraudulent election in Russia’s post-Soviet history. The Kremlin has praised it as a “triumphal referendum on confidence in President Putin.”

Last week, opposition activists were detained and their apartments were searched. A former investigative journalist, Ivan Safronov, was arrested and charged with treason without any evidence presented publicly. And a young spokesman for a medical group that has blown the whistle on the Kremlin’s poor COVID-19 response was arrested and drafted into the army.

Furgal is perhaps the highest-profile victim of the Kremlin’s crackdown, considering his standing in government. And in a piece published by the Carnegie Moscow Center over the weekend, political commentator Andrey Pertsev argued that the case — and indeed the broader wave of repression — shows that the Putin regime no longer sees a need for a loyal opposition or even public consent in its rule.

“Voting on the constitutional amendments appears to be the last point where the mood and preferences of citizens were somehow taken into account. The Kremlin will achieve the desired election results by other methods — electronic voting, multiday voting, voting anywhere and at any time,” Pertsev concluded, referring to massive fraud allegations around the vote.

“You may be against it, but no one is asking what you think anymore.”

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The Kremlin rarely caves in to public pressure, so it seems unlikely that Furgal will return to his post. On Monday the Liberal-Democratic Party chief, Vladimir Zhirinovsky, floated what appeared to be a way for the Kremlin to save some face: appoint a different party member as governor of Khabarovsk. The party has even forwarded three names.

But Zhirinovsky struck a more defiant tone Tuesday in a tweet that declared that “the arrest of Sergei Furgal is a mistake by the Kremlin.”

“The unrest in Khabarovsk will not subside until [he] returns to the region. He will return and continue his work as governor. If I were in the president’s position I would remove the envoy [and] place one man at the head of the Far East — Furgal,” Zhirinovsky wrote.

Zhirinovsky’s sentiments appear to be in line with those of some of the protesters, who for the moment appear to be undeterred and resolved to keep marching.

“While we ourselves do not know what the outcome will be,” the office worker said, “demonstrations are scheduled for the coming week. We do not know whether or not this will help, whether Furgal will be freed or not or whether things will get better or worse from these actions. But the people are not going to stand down — everyone is riled up.”