Refugees are seen shortly after arriving on an inflatable boat crossing the sea from Turkey to Lesbos on March 12, 2016 in Mytelene, Greece | Alexander Koerner/Getty Images ‘Dramatic’ drop in migrant arrivals on Greek islands EU-Turkey refugee deal a factor in fall in migrant numbers, says EU border agency.

Fewer than 2,700 migrants arrived on the Greek islands in April, a fall of 90 percent from the previous month, EU border agency Frontex reported Friday, citing the EU-Turkey refugee deal as one factor behind the drop.

"Stricter border policies applied by the former Yugoslav Republic of Macedonia at its border with Greece" also contributed to what Frontex Executive Director Fabrice Leggeri labeled a “dramatic” drop in migrant arrivals to the islands.

"The total for all of April is well below the number of people we often saw reaching just the island of Lesbos on a daily basis during last year’s peak months,” Leggeri said.

Under the European Union's deal with Ankara, every migrant reaching the Greek islands is returned to Turkey in exchange for the EU taking Syrian refugees direct from Turkey, and granting extra aid, visa-free travel rights and progress in the country's EU membership application.

Syrians made up the largest proportion of those arriving on the islands in April, followed by people from Pakistan, Afghanistan and Iraq.

Italy has expressed concern that the EU’s deal with Turkey will force more people to attempt the dangerous Central Mediterranean crossing. However, migrants taking the Central Mediterranean route in April fell by 13 percent on the March figure, to 8,370. That is almost 50 percent down on the April 2015 figure, according to Frontex.