With Russia's invasion of Ukraine entering its fourth day, tens of thousands of people across Europe have gathered in protest of the war, calling on Russian president Vladimir Putin to put an end to the conflict as hundreds of thousands of Ukrainian refugees flood neighboring countries.

APTOPIX Germany Ukraine Invasion

People walk down the street. Ahead of a rally against Russia. This photo was taken by Markus Schreiber.

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Tens of thousands of people have been protesting in central Berlin in recent days, with mass gatherings shutting down parts of the city's public transportation service.

The protests began prior to Russia declaring a military operation in Ukraine.

Thousands gathered in central Madrid Sunday with protest signs ranging from "Peace" to "Putin" and "My grandmother is really angry."

In addition, gatherings were held in Rome, Lisbon, and London.

There were 46 Russian cities that held on Sunday, with the total number of people arrested in Russia increasing to over 5,000.

Russia Ukraine Invasion

Police detain a demonstrator during protests.

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Russia Ukraine Invasion

Police detain a demonstrator in Moscow. In this photo, Denis Kaminev.

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Vaitcan Pope Ukraine

Faithful display Ukrainian flags during Pope Francis Angelus noon prayer. The photo was taken by Gregorio Borgia.

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Russia Ukraine Invasion

A man holds a poster in Moscow that reads "No War" In this photo, Denis Kaminev.

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Britain Ukraine Invasion

The people descend on Trafalgar Square to attend a protest. This photo was taken by Albert Pezzali.

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Britain Ukraine Invasion

People descend to attend a protest in London, as Ukrainian flags wave in Trafalgar Square.

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CZECH-UKRAINE-RUSSIA-CONFLICT-DEMONSTRATION

The protesters took part in a demonstration at the Venceslas square in the Czech Republic.

AFP via Getty Images