In Russia, after the attack on Ukraine, the first resistance is stirring.
Police arrested several people during anti-war protests in central Moscow, the RIA news agency reported on Thursday.
Police cordoned off Pushkin Square, a Reuters reporter reported.
The opposition activist Marina Litvinovich had previously been arrested, as she confirmed to the Reuters news agency.
"I was arrested on the way home," wrote the messenger service Telegram.
Litvinovich, who lives in Moscow, had previously called on her compatriots to protest against the attack.
"Today at 7 p.m. in the centers of our cities.
Russians are against war!” she wrote in a Facebook post.
“We will clean up this mess in the years to come.
Not just us.
But also our children and grandchildren.”
The human rights organization OVD-Info counted 1,400 arrests in 51 Russian cities.
In the Russian capital, Moscow, about 1,000 people chanted "No to the war!" in the central Pushkin Square.
Many Russians feel close ties to the Ukrainians, and there are often family ties.
Demonstrators are said to have been beaten during the arrests.
Many protesters had tears in their eyes at the sight of the invasion of Ukraine ordered by Kremlin chief Vladimir Putin.
It was the biggest protest since the beginning of last year, when Kremlin opponent Alexei Navalny was arrested in Moscow after his return from Germany.
Navalny had just survived an attack with the chemical warfare agent Novichok in Russia and was then treated in Germany.
He blames Putin for the assassination.
"I am against war," said the opponent of Putin, who was imprisoned in the penal camp and threatened with 15 years in prison in a new controversial trial.
The attack on Ukraine is fratricide and criminal.
“The Kremlin gang kicked him loose so they could keep stealing.
They kill to steal,” he stressed in court on Thursday.
Criticism of the attack ordered by President Vladimir Putin has also come from the Fridays for Future movement in Russia.
"In a situation where the world is suffering from climate, environmental and other crises, war will only exacerbate these crises but will not solve them," the activists wrote on Twitter.
"In our time, all conflicts must be resolved through diplomacy and not through the blood of civilians in other countries." They pledged "our solidarity and support" to the Ukrainian comrades-in-arms.
Russian authorities have warned people in their own country against protests in the face of the invasion of Ukraine.
"Due to the tense foreign policy situation," social networks are calling for unauthorized rallies, the investigative committee, the Interior Ministry and Moscow's public prosecutor announced on Thursday.
The Interior Ministry threatened arrests.
Russian security forces are known for often cracking down on opposition demonstrators.