ISTANBUL: Turkey needs to stop or significantly reduce the number of illegal migrants crossing into Europe and a readmission agreement between Ankara and Brussels must go into full effect by June 1, an EU envoy said on Friday.

"A very important date will be the first of June, when all provisions of the Turkey-EU readmission agreement will have to apply and be fulfilled," Hansjorg Haber, head of the EU delegation to Turkey, told a news conference in Istanbul.

"In the meantime, it is important to improve the application of the existing bilateral readmission agreement with Greece and Bulgaria. Then Turkey needs to stop or very, very significantly reduce the irregular departures of refugees and migrants from its Aegean coastline to Greek islands."

An EU official said Brussels and European governments were counting on Turkey substantially reducing the numbers of people reaching Greek islands within days and that those who did take to boats could now be deported and accepted back by Turkey under an existing return agreement between Athens and Ankara.

Haber also said that an October deadline for easing restrictions on travel to Europe for Turks was "not automatic".