EU-Turkey-deal
Turkish Prime Minister Ahmet Davutoglu speaks at a news conference at the end of a EU-Turkey summit in Brussels on March 8, 2016. REUTERS/Yves Herman

The United Nations refugee agency said on Tuesday that the European Union's "quick fix" deal to send back refugees en masse to Turkey would contravene their right to protection under European and international law.

European Union leaders welcomed Turkey's offer on Monday to take back all migrants who cross into Europe from its soil and agreed in principle to Ankara's demands for more money, faster EU membership talks and quicker visa-free travel in return.

Vincent Cochetel, Europe regional director of the U.N. High Commissioner for Refugees (UNHCR), said that Europe's commitment to resettle 20,000 refugees over two years, on a voluntary basis, remained "very low".

"The collective expulsion of foreigners is prohibited under the European Convention of Human Rights," Cochetel told a news briefing in Geneva.

"An agreement that would be tantamount to a blanket return to a third country is not consistent with European law, not consistent with international law," he said.

Europe had not even fulfilled its agreement last September to relocate 66,000 refugees from Greece, redistributing only 600 to date within the bloc, Cochetel said earlier.

"What didn't happen from Greece, will it happen from Turkey? We'll see, I have some doubts," he said on Swiss radio RTS.

Turkey is home to nearly 3 million Syrian refugees, the largest number worldwide, but its acceptance rates for refugees from Afghanistan, Iraq and Iraq were "very low", about 3 percent, Cochetel said.

"I hope that in the next 10 days a certain number of supplementary guarantees will be put in place so that people sent back to Turkey will have access to an examination of their request (for asylum)."

UNHCR spokesman William Spindler said: "Legal safeguards would need to govern any mechanism under which responsibility would be transferred for assessing an asylum claim."

The U.N. Children's Fund (UNICEF) voiced deep concerns about the agreement, noting that "too many details still remain unclear".

"The fundamental principle of 'do no harm' must apply every step of way," UNICEF spokeswoman Sarah Crowe told the briefing.

"That means first and foremost that children's right to claim international protection must be guaranteed. Children should not to be returned if they face risks including detention, forced recruitment, trafficking or exploitation."