More than 4,300 people were detained at anti-war protests across Russia on Sunday, rights groups and Russian authorities say.
Some 1,700 people were detained in Moscow alone, Ria news agency reports, citing the interior ministry.
The OVD-Info rights group says detentions took place in 53 cities.
Although protests have become increasingly restricted in recent years, numerous rallies have taken place across Russia since the invasion.
In the last 11 days, more than 10,000 people have been detained at protests, OVD-Info says.
“The screws are being fully tightened – essentially we are witnessing military censorship,” Maria Kuznetsova, OVD-Info’s spokeswoman, told Reuters news agency from Tbilisi in Georgia.