MOSCOW (AP) — The former mayor of Russia's fourth-largest city was arrested Wednesday on charges of discrediting the country's military, part of a crackdown on critics of Moscow's military action in Ukraine.

Police arrested Yevgeny Roizman, 59 who served as the mayor of Yekaterinburg in 2013-2018, following searches at his apartment and office.

Roizman told reporters he was charged under a new law adopted after Russia sent troops into Ukraine on Feb. 24. He faces up to five years in prison if convicted.

Russian courts fined Roizman three times earlier this year on similar charges, paving the way for a criminal case the law authorizes for repeat offenses.

Roizman, a sharp critic of the Kremlin, is one of the most visible and charismatic opposition figures in Russia. During his tenure as mayor, he enjoyed broad popularity in Yekaterinburg, a city of 1.5 million in the Ural Mountains.

Shortly after his arrest, a few local residents picketed in his support.

Cautious words of support also came from Roizman's longtime political rival, the governor of Russia's Sverdlovsk region.

“We used to be and continue to be political opponents. The law is the law. But, like any person, he deserves fairness and respect, and I hope he gets them,” Gov. Yevgeny Kuyvashev said in a video statement posted on Telegram.

While police escorted him from his apartment, Roizman told reporters that he would likely be brought to Moscow for investigation. He said that the criminal charges against him were triggered by him calling what the Kremlin describes as a “special military operation” in Ukraine an invasion.

"I was saying that everywhere, and I will say it now,” the politician added.

Days after Russian President Vladimir Putin sent troops into Ukraine on Feb. 24, Russia's Kremlin-controlled parliament controlled approved legislation that outlawed disparaging the military and the spread of “false information” about the military operations in Ukraine.

Russian courts have increasingly handed out fines and, occasionally, prison terms to critics of Moscow's action in Ukraine.

According to Net Freedoms, a legal aid group focusing on free speech cases, there were 79 criminal cases as of mid-August on charges of spreading false information about the military and up to 4,000 administrative cases on charges of disparaging the armed forces.

Pavel Chikov, a leading Russian human rights advocate, said Wednesday that Russian courts have so far heard 3,500 administrative cases for discrediting the military and found most defendants guilty. All of them could face criminal charges like Roizman, if they speak out again against Russia's operation in Ukraine, Chikov noted.

Until his arrest, Roizman remained one of the most visible opposition figures in Russia who had not been been jailed or fled the country under pressure from authorities. Two other prominent opposition politicians, Ilya Yashin and Vladimir Kara-Murza, were arrested under the same law as Roizman and face up to 10 years in prison, if convicted.

Similar charges were recently brought against eight close associates of imprisoned opposition leader Alexei Navalny. All of them have left Russia after they became the subjects of multiple criminal investigations.