Demonstrators hold banners in support of refugees as they march through central London on March 19, 2016
London (AFP) - Protestors voicing their support for migrants took to the streets of European capitals Saturday, the day after the EU and Turkey sealed a deal designed to tackle the continent's biggest migration crisis since World War II.
Thousands of people marched in London, Athens, Barcelona, Vienna, Amsterdam and several Swiss cities as Greece rushed to put in place the measures needed to enforce the deal sealed at a Brussels summit Friday.
Under the deal, all migrants arriving in Greece from Turkey from midnight on Sunday will face being sent back to Turkey.
The EU will take in one Syrian refugee from Turkish soil in exchange for every Syrian returned from Greece in a move designed to discourage people risking their lives by crossing the Aegean Sea in smugglers' boats.
In London, approximately 4,000 people joined a protest carrying placards with slogans like "Refugees welcome here" and "Stand up to racism".
Callum Nash, a web designer, said he had come "to show support and solidarity for migrants, for refugees, coming from Syria".
Emiliano Mellino, a financial journalist from Argentina, added: "The situation right now in Syria, in Lebanon, in Jordan, in Turkey... the number of refugees they have, and the pressure those countries have, is incredible and Europe is not letting in enough people."
In Athens, police said 1,500 people took to the streets while media put the figure at 3,000.
The protestors, who included many Afghan refugees, particularly women and children, chanted "Open the borders" and "We are human beings, we have rights".
"We're calling on the Greek government to stop aligning itself with the EU's anti-refugee policies," said pro-migrant activist Thanassis Kourkoulas.
Another protest in the northern city of Thessaloniki drew around 500 people, according to police.
Several thousand people marched in Barcelona carrying banners with slogans such as "No person is illegal", while the figure was roughly 2,500 in Vienna. Around 1,500 people also took to the streets of Amsterdam.
In Geneva, more than 600 people joined the protests to support the right of migrants to remain. Some were particularly protesting against the housing of refugees in bunkers.
There were also smaller protests in other Swiss cities such as Zurich and Lucerne.