Russian riot police beat protesters with batons and hauled away dozens on Sunday after skirmishes broke out at a demonstration in Moscow against Vladimir Putin on the eve of his return to the presidency. (Denis Sinyakov/Reuters)

Thousands of political protesters turned out in Moscow on Sunday, the day before Vladimir Putin’s presidential inauguration, and were met with a menacing and violent police response.

The authorities showed that they were in a far less tolerant mood than they had been during anti-government demonstrations over the winter, as squads of police officers in riot gear made repeated forays into the taunting and defiant crowd, striking out with nightsticks and detaining more than 450 people. But the protest also indicated that despite Putin’s election victory in March, the opposition hasn’t petered out and isn’t going away.

The street fighting casts a shadow on Putin’s inauguration festivities Monday. In recent months, Russians have seen the emergence of a vocal and significant opposition to his rule. But as Putin assumes the presidency for the third time, a new question arises: How violent will things get?

Plastic bottles, chunks of asphalt and red highway flares rained down on police officers after they confronted angry young members of the Left Front, who tried to break away from the main crowd and march on the Kremlin. Police later said 27 people were injured, including seven demonstrators. A photographer who fell from a roof died.

During the winter, the protests — triggered by allegations of election fraud — had been almost entirely law-abiding and of good cheer. But at Sunday’s march, the frustration — over the prospect of Putin’s beckoning six-year term — spilled out. And the police were ready with a more aggressive response. Later, investigators said they were opening criminal cases against some of the protest organizers.

Among those detained were three prominent opposition figures: Sergei Udaltsov, leader of the Left Front; Alexei Navalny, an ­anti-corruption blogger; and the veteran liberal politician Boris Nemtsov. After the main rally, at Bolotnaya Square, had ended, hundreds of demonstrators marched unhindered down Ordinka Street to protest outside the police station where the three were thought to be held. Among those marching was Yevgenia Chirikova, a prominent environmental activist, who said she was outraged by the aggressive and brutal police tactics.

Three of the main news sources for anti-government Russians — Dozhd TV, an Internet-based independent channel; Ekho Moskvy radio; and the Kommersant newspaper and radio organization — said they were under heavy denial-of-service cyberattacks Sunday. Putin spokesman Dmitry Peskov said government Web sites also had come under attack.

The permit for Sunday’s two-mile march allowed only 5,000 participants, but an estimated 20,000 or more showed up. Alexander Belousov, 47, was among those who had feared an anemic turnout. “I’m not alone,” he said with satisfaction, as he surveyed the crowd along the banks of the Moscow River. “I haven’t surrendered. And what has started can’t be stopped.”

Self-respect, he said, had driven people to attend the rally, even though there is no prospect of immediate political change. “I believe Putin will stay six years. I’m trying to be realistic. But what happens next depends on the people. They have to organize themselves.”

Olga Selivanova, 45, had a sign taped to her white umbrella that read: “Dearest daughter, buy milk, lunch is in the refrigerator. I’m at the demonstration. I want to return democracy to Russia. I’ll be late. Your mama.”

She actually has two daughters, she said, ages 16 and 12. Selivanova became politically active after they told her that they saw no future for Russia. Now, she said, she is among those asking questions and demanding answers. “We’re learning to be citizens,” she said.

Natalia Pelevine was drinking coffee with two other activists at a Starbucks off Tverskaya Street near the Kremlin on Sunday afternoon when they noticed what appeared to be plainclothes police officers watching them. Pelevine said she and her friends were discussing holding an impromptu illegal demonstration at a plaza near the Kremlin. After about an hour, she said, the plainclothes officers, by then joined by uniformed police, burst in and tried to drag them off.

“It was pretty brutal,” Pelevine said, surmising that the police had been eavesdropping on her phone conversations and following her. Pelevine, who is Russian but fluent in English, started screaming in Russian and English, attracting the attention of a passing journalist. The police finally let her go but detained her friends. One of them was later released, but she said the other may face serious charges. He is Vadim Korovin, who was previously arrested Feb. 29 as he took tents out of his car to give to would-be protesters.

But no police officers were in sight when protesters at the riverbank surrounded a van from NTV, a television company that has broadcast the most vehement and, many say, spurious reports about the opposition. A few people, shouting “Shame! Shame!,” plastered the truck’s windshield with posters promoting another anti-government rally. Others pelted it with trash. After about 15 minutes of captivity, the truck limped off with one tire flattened.