Thousands protest in European capitals to support migrants

Protesters voicing support for migrants took to the streets of European capitals on 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 on Friday.

Under the deal, all migrants arriving in Greece from Turkey after midnight on Sunday will face being sent back to Turkey. The EU will take in one Syrian refugee from Turkish soil in exchange for each Syrian returned from Greece in a move designed to discourage people risking their lives by crossing the Aegean Sea in smugglers' boats.

Athens signalled on Saturday that implementation could occur only gradually, with key details still to be worked out on how migrants newly arriving from Turkey will be processed and returned, the Associated Press reported.

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."

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. Dozens of people also took to the streets of Amsterdam.

In Athens, police said 1,500 people took to the streets while media put the figure at 3,000. The protesters, 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.

Prime Minister Alexis Tsipras met ministers and senior officials involved in the migration crisis, hours after the deal was reached in Brussels to send back migrants arriving on the Greek islands to Turkey, starting Sunday, AP said.

Hours before that implementation was due to start, it remained unclear how migrants would be sent back, AP said. Greek officials had previously suggested that the European border protection agency Frontex could escort chartered private vessels back to Turkey.

Yiannis Balafas, the deputy interior minister, said swift screening procedures in the Greek islands would require additional staff promised by the European Union, AP said.

"[Migrants] will be returned after they have been swiftly processed. That is why we need the technical assistance," Balafas told private Mega television.