MOSCOW — Tens of thousands of protesters held anti-corruption rallies across Russia on Monday in a new show of defiance by an opposition that the Kremlin had once dismissed as ineffectual and marginalized.

More than 1,000 were arrested – including opposition leader and protest organizer Alexei Navalny, who was seized outside his Moscow residence while heading to the rally in the city center and sentenced to 30 days in jail several hours later.

The Moscow protest was the most prominent in a string of more than 100 rallies in cities and towns stretching through all 11 of Russia’s time zones – from the Pacific to the European enclave of Kaliningrad – with many denouncing President Vladimir Putin.

Thousands of angry demonstrators thronged to Tverskaya Street, a main avenue in the capital, chanting “Down with the czar” and singing the Russian national anthem.

The protests coincided with Russia Day, a national holiday that this year brought out historical re-enactors, some of them dressed in medieval costumes.

At one point, the Moscow demonstration featured an unlikely scene of about 5,000 protesters rallying next to an enclosure with geese, a medieval catapult and bearded men in homemade tunics and carrying wooden shields.

The re-enactors watched the rally before riot police broke up the crowd and randomly seized the protesters.

Over 800 people were arrested in Moscow, while in St. Petersburg, about 500 were forced into police buses at an unsanctioned rally that drew up to 10,000 people.

Navalny was taken to court Monday evening and sentenced shortly after midnight for repeated violations of the law on public gatherings.

“The scope of rallies was amazing, and so many people came out,” Navalny told reporters shortly before he was sentenced.

In his trademark humor, Navalny lamented on Twitter shortly before he was led out of the courtroom that he would have to skip a Depeche Mode concert while he is in jail.