Pavel Golovkin/Associated Press
Police officers detained the opposition leader Aleksei Navalny during a rally in Lubyanka Square in Moscow on Saturday.
MOSCOW — Forcing a showdown with the government of President Vladimir V. Putin, leaders of the Russian political opposition took to the streets on Saturday afternoon for an unsanctioned demonstration in a symbolic square in Moscow that is home to the headquarters of the federal security services as well as a monument to victims of Soviet political repression.
Bundled up against the frigid cold and wind, with the temperature hovering at about 5 degrees Fahrenheit and the late December light slashing across a clear sky, about 2,000 demonstrators gathered in Lubyanka Square, not far from the Kremlin. They were met by a huge contingent of riot police officers, who quickly cordoned off the area and began making arrests.
The protest without a permit was a pointed act of defiance, particularly by the two most prominent opposition leaders: Aleksei Navalny, an anticorruption activist, and Sergei Udaltsov of the Left Front, a radical socialist group. Mr. Navalny and Mr. Udaltsov face a growing number of criminal charges and have lived for weeks with the prospect of imminent arrest.
Mr. Udaltsov was seized by the riot police moments after he arrived, at about 3 p.m., and hustled into a police van. “I am not violating any laws,” he shouted as he was taken away. “Russia will be free.”
Mr. Navalny, by contrast, arrived surrounded by a large scrum of photographers and worked the crowd like a politician on a rope line, shaking hands with supporters. He seemed buoyant and carefree and said, “O.K., let’s stand here awhile.” The mob around him seemed to forestall his arrest, but not for long. He was detained about an hour after his arrival.
Other well-known opposition leaders were given no leeway. A television personality, Kseniya Sobchak, and a liberal activist, Ilya Yashin, were arrested immediately after emerging from a nearby cafe. About an hour and a half later, the police began arresting dozens of rank-and-file demonstrators.
The crowd was a fraction of the size of previous rallies this year, suggesting that interest may be waning. The inability of the opposition leaders and the authorities to agree on the terms for a protest permit also suggested that each side’s resolve might be hardening.
By attending the rally, demonstrators showed they were unbowed by a law signed by Mr. Putin in June that imposes steep fines — of more than $9,000 for participants and more than $18,000 for organizers — for taking part in unsanctioned protests.
“Today we showed the authorities that we have principles and dignity, that they cannot forbid us from taking a walk in our own city, because we will come anyway,” said Dmitri Gudkov, one of a small number of Russian lawmakers to support the opposition openly. “There is still protest and we want change, and they can’t frighten us with detention or pressure or searches or arrests or anything else.
“If you want to avoid massive acts of protest, initiate reforms, my friends, and the people will not come out to protests.” By swiftly arresting the main opposition leaders, the authorities seemed to calculate that they would face minimal public reaction, though that is likely to be determined by how severely the opposition members are treated within the judicial system.
The law that increased fines is one of numerous steps Mr. Putin’s government has taken to clamp down on political dissent in the year since evidence of fraud in parliamentary elections last December set off a series of large street demonstrations here.
The early protests were marked by a certain giddiness, as many middle-class Muscovites embraced the newfound spirit of political activism. But with Mr. Putin’s return to the presidency, after a solid victory in elections last March, the space for political dissent has contracted.
The authorities have opened numerous criminal investigations into leaders of the political opposition, carried out repeated searches of their homes and businesses, and filed charges that in some cases could lead to lengthy prison sentences.
On Friday, the authorities announced yet another criminal investigation of Mr. Navalny, accusing him and his brother, Oleg, who is a post office employee, of a strange scheme to steal money in business deals by overcharging for the services of a private courier company.
