Russia on Thursday pointed to the storming of the US Capitol building as evidence of America's decline, with officials saying its out-of-date electoral system and deep divisions had left its democracy "limping on both feet".

Under banners reading "Storm of the Capitol" and "Chaos in Washington", Russian state television showed rolling images of mobs of Donald Trump supporters breaking down barricades and swarming the Congress building on Wednesday, as security forces fired tear gas and police drew guns inside.

Congress formally certified Joe Biden as the next president despite the unrest, but many in Moscow said the stunning events had exposed America's democratic failings.

"The electoral system in the United States is archaic, it does not meet modern democratic standards... and the American media have become an instrument of political struggle," foreign ministry spokeswoman Maria Zakharova said on Facebook.

"This is largely the reason for the split in society now observed in the United States."

Moscow has long bristled at US criticism of the state of Russian democracy under President Vladimir Putin, accusing Washington of hypocrisy and condescension.

 'Rock bottom' 

Often echoing the kind of language used against Russia, officials in Moscow said the United States was no longer in any position to lecture other countries on freedom and democracy.

"It is clear that American democracy is limping on both feet," said Konstantin Kosachyov, the chair of the Russian upper house's foreign affairs committee.

"The celebration of democracy has ended. It has, unfortunately, hit rock bottom, and I say this without a hint of gloating.

"America no longer charts the course and so has lost all right to set it. And, even more so, to impose it on others."

The Kremlin has itself been accused of fostering US divisions with a campaign of interference and disinformation, including alleged attempts to disrupt the 2016 election in Trump's favour that prompted an FBI investigation.

With Russia celebrating the Orthodox Christmas holiday there was no reaction to the events in Washington from the Kremlin.

But pro-Kremlin lawmakers jumped on the unrest.

"The United States certainly cannot now impose electoral standards on other countries and claim to be the world's 'beacon of democracy'," the foreign affairs chief in the lower house, Leonid Slutsky, told Russian news agencies.

He said Washington was suffering from a "boomerang" effect after having promoted "colour revolutions" around the world, like anti-Moscow uprisings in Ukraine and Georgia and the recent protests in Belarus.

Russian opposition leader Alexei Navalny, recovering in Germany from poisoning with a nerve agent he blames on the Kremlin, said Putin's backers would use the unrest to promote his rule.

"The Putinites will cheer at the conflicts in the United States and extol 'Putin's stability'," he said on Twitter.

 'Like the Wild West' 

Navalny's top ally Lyubov Sobol said the fact that Congress had finally confirmed Biden was evidence of the strength of US democracy.

"For Russia, it is of course inconceivable that the current president of America... is trying to stay in power for a new term but cannot," she said on Twitter.

"Here it is, the power of democracy."

Washington has been a fierce critic of moves by Putin to clamp down on dissent. Moscow says the United States cynically uses such claims to pursue its agenda and maintain its global position.

Tensions between the Cold War-era rivals have hit new highs in recent years, with a raft of US sanctions imposed on Russian officials, disputes over arms control treaties and American accusations of major Russian hacking attacks.

On the snow-covered streets of Moscow, ordinary Russians were largely bemused by the events in Washington.

"It looks quite ridiculous," said pensioner Elena Kukharsakaya. "He (Trump) is acting like a rat who is kicked out of the house and keeps coming back."

Sergey Khrulev, 64, said the images reminded him of old American movies.

"It's like the Wild West: the one with the colt is the strongest," Khrulev said.

By Michael Mainville and Nikolay Korzhov