A boy bundled up in a blanket stands on a dock as migrants and refugees arrive on the Greek island of Lesbos while crossing the Aegean Sea from Turkey on March 2, 2016. Getty Images

European Union leaders approved a migration deal with Turkey on Friday, igniting a backlash from many human rights groups worldwide. Groups including Doctors Without Borders and Amnesty International have argued that the deal would likely produce additional human suffering and might be illegal under international law.

Terms of the deal call for refugees, many of whom are fleeing war-torn Syria and are crossing the Aegean Sea by raft or boat, to be sent to Turkey. In exchange, European Union nations would take in a relative small number of Syrians from Turkey. While full details of the plan have yet to emerge, EU leaders have been discussing a detailed package of cash and incentives. The deal aims to slow down the number of refugees coming to Europe by way of illegal smuggling, but human rights groups are calling foul.

Thousands of people in more than 50 cities across Spain protested the pact Thursday, and activists urged the government of Prime Minister Mariano Rajoy to veto it, arguing that it violates human rights. Labeling the deal as illegal, immoral and shameful, protest organizers contended that the EU initiative breaks the Universal Declaration of Human Rights, the Charter of Fundamental Rights of the European Union and the Geneva Convention for refugees.

“We are against decisions that have been taken by the EU and their states; that are unable to find a satisfactory decision compatible with the drama of the situation of those who are living, the millions of people who are gathered in Turkey, Lebanon, Jordan, at the gates of the EU, where walls and fences are raised to prevent entry,” European Trade Union Confederation President Ignacio Fernandez Toxo told Ruptly.

Syrian refugees are helped from an inflatable boat with other refugees after crossing the sea from Turkey to the Greek island of Lesbos, on March 9, 2016. Getty Images

Amnesty International also urged rejection of the deal, arguing that Turkey is far from a safe country for refugees. The organization stated that Turkey has repeatedly pushed Syrians back into the war zone and closed borders to others seeking to flee the war-torn country, while current refugees in Turkey are struggling to find work and educate their children.

“In their determination to sidestep their responsibilities in the face of the biggest global refugee crisis since World War II, EU leaders have been mute in their response to these trends in the misguided hope of securing Turkey’s cooperation in stopping the boats,” wrote Amnesty International.

Doctors Without Borders argued that access to safety in Turkey is not guaranteed for people fleeing Syria, according to a press release.

“The voluntary humanitarian admission scheme put forward for Syrians in Turkey is not based on refugees’ needs for assistance and protection but on Turkey’s ability to stop 'migration' to Europe,” said Aurélie Ponthieu, humanitarian affairs adviser for Doctors Without Borders, according to a blog post. “At a time when millions of people in the world are displaced, it is shameful that the only safe passage offered by the EU is conditional to the number of people they can send back.”

Syrian refugees are helped from an inflatable boat with other refugees after crossing the sea from Turkey to the Greek island of Lesbos, on March 9, 2016. Getty Images

Filippo Grandi, the U.N. high commissioner for refugees, has questioned the legality of the deal. The senior U.N. official reportedly said he was very concerned that it could leave Syrian refugees unprotected and at risk of being sent back to war zones. Grandi argued that asylum seekers should only be returned to other states if they were guaranteed that they would not be sent back to the places they fled, and that the country of return also had to ensure that the asylum seekers had access to work, healthcare, education and social assistance.

British Foreign Secretary Philip Hammond received a letter saying that Kurds fleeing Iraq, Syria and Turkey could face a “very dangerous situation” if they were forced to return to Turkey under the terms of the EU deal, the Guardian reported. In the letter, Liberal Democrat foreign affairs spokesman Tom Brake noted that Kurds faced persecution in Turkey.

"Many Kurds have understandably fled Iraq and Syria as a result of the destruction of communities by Daesh [Islamic State] in the north of Syria and Iraq. The increase in assaults by Turkish forces against the Kurdistan Workers’ Party (PKK) has led to more Kurds trying to reach Europe,” wrote Brake in a letter to Hammond and Home Secretary Theresa May, the Guardian reported. "I am concerned that Kurds will potentially be sent back to Turkey as a result of the proposals agreed between the EU and Turkey, which will lead to a very dangerous situation for Kurdish people. I would therefore like to know what the government is doing to ensure that Kurds will not be put in danger by being sent back to a hostile Turkey."