The head of the UN refugee agency said it is too early to evaluate the EU-Turkey deal and that safeguards need to be implemented. Her comments come just a few days after Greece deported hundreds of migrants to Turkey.

"It may take a little bit of time. This is why we were hoping for a bit more time to put these safeguards in place but we also fully appreciate that there was a political imperative to fix a deal and implement it and you know, sometimes agreements you have to start implementing to make them better," said Filippo Grandi, UN High Commissioner for refugees.

Grandi said the recent crisis has shown that Europe needed a more cooperative system for asylum. He acknowledged that Greece, hindered by a huge debt crisis, was struggling to cope and needed assistance.

Human rights groups on the ground said facilities were still ill-equipped and many migrants were kept waiting.

The UNHCR chief said those who seek asylum in Greece should be given a fair hearing. The problem is that it requires capacity that the Greek asylum system does not have yet.