The Kremlin on Sunday accused the United States of interfering in Russia's domestic affairs and downplayed the scale of the weekend's protests, when tens of thousands rallied in support of jailed opposition politician Alexei Navalny.
More than 3,500 demonstrators were detained in protests across the country on Saturday, with several injured in clashes with police in Moscow, following Navalny's call to rally against President Vladimir Putin's 20-year rule.
The West has widely condemned the "harsh tactics" used against demonstrators, with French Foreign Minister Jean-Yves Le Drian saying Sunday the mass arrest of protesters was "an intolerable affront" and a "slide towards authoritarianism".
Polish President Andrzej Duda has called for the European Union to step up sanctions against Russia over the treatment of Navalny, the Financial Times reported Sunday.
"The only way to (avoid conflict) is to force international law to be observed. The only way to do this without rifles, cannons and bombs is via sanctions," Duda told the FT.
The Polish leader also said EU foreign affairs chief Josep Borrell should re-consider plans to visit Russia next month unless Navalny is released.
EU foreign ministers are due to consider their response to Navalny's detention on Monday, with Borrell saying the "next steps" will be discussed.
Putin's spokesman Dmitry Peskov on Sunday accused the US embassy of interfering in Russia's domestic affairs after the mission distributed a "demonstration alert" to US citizens in Russia recommending they avoid protests.
"Of course, these publications are inappropriate," Peskov told a state TV channel. "And of course indirectly, they are absolutely an interference in our domestic affairs."
A US mission spokeswoman said US embassies and consulates around the world routinely issue safety messages to US citizens.
"This is a common, routine practice of many countries' diplomatic missions," she told AFP on Sunday.
The US embassy in Moscow on Saturday said that Washington supported "the right of all people to peaceful protest, freedom of expression".
- Protests in over 100 cities -
Peskov also accused protest organisers of seeking to "rock the boat" and said the number of people who had demonstrated paled in comparison to Putin supporters.
"A lot of people vote for Putin," Peskov said, pointing to last year's constitutional plebiscite that allowed 68-year-old Putin to remain in power until 2036.
Navalny, Putin's most prominent critic, was arrested on returning to Moscow last weekend following months of treatment in Germany for a near-fatal poisoning with a Soviet-designed Novichok nerve agent.
He then called for Saturday's unauthorised protests, which took on an unprecedented geographic scale, spanning more than 100 cities.
Around 20,000 people protested in Moscow and more than 10,000 in Saint Petersburg, according to estimates from AFP journalists, with rallies also held in numerous countries including France and Lithuania.
Leonid Volkov, the head of Navalny's regional network, praised the turnout.
"I am certainly proud, very impressed and inspired," Volkov told AFP. Navalny's team is hoping to stage another rally next weekend.
Many at the protests said they were angered by the findings of a Navalny investigation into an opulent Black Sea property allegedly owned by Putin.
Peskov said the luxury mansion on the Black Sea was "private" property and had nothing to do with Putin.
- Protester in intensive care -
Moscow officials said that 29 people received medical assistance in hospitals and were released.
Saint Petersburg prosecutors said they were probing violations on "the part of law enforcement" and the use of force against a woman.
The statement was released after local media published a video showing a middle-aged woman falling to the ground after being kicked by riot police.
In the video, a woman -- identified as Margarita Yudina -- is seen asking three policemen in full riot gear why they were detaining a young unarmed protester. One of the policeman then kicks her in the stomach.
The Investigative Committee, which probes major crimes, said it had launched criminal inquiries in Moscow over the use of violence against law enforcement, hooliganism and property damage.
The OVD Info monitor said police seized at least 3,521 protesters, with 1,398 people detained in Moscow and 526 in Saint Petersburg.
The head of the Kremlin's human rights council, Valery Fadeyev, said most of those detained in Moscow had been released.
He also defended the detentions, saying the protests were illegal and took place during a coronavirus pandemic. "I see no violations whatsoever," he said.
Navalny, who rose to prominence a decade ago, accuses the FSB security agency of seeking to poison him on Putin's orders.
He is the target of several criminal probes and supporters fear authorities are planning to sentence him to a long prison term.