The European Union's top migration official said on Wednesday a deal with Ankara on refugees was beginning to have an effect and would eventually be scaled up, after the first irregular migrants were returned to Turkey this week.

"We are still at the beginning, the numbers are very low," EU Migration Commissioner Dimitris Avramopoulos told a news conference. "But it's better to start working slowly. I believe in the course of time we will scale up... It's a good start."

Avramopoulos was in Ankara earlier this week to demand that Turkey introduces legal protection for asylum-seekers before the EU began sending them back. The Greek diplomat said that was still indispensable for larger-scale returns to start.