At least 11 Syrian refugees have drowned after a boat capsized in the Aegean Sea, off the western coast of Turkey, according to Turkish authorities.

The inflatable boat was carrying at least 20 people and was en route to the Greek islands when it sank off the coast of Kusadasi district in western Aydin province, the Turkish coastguard said in a statement on Friday.

"Nine migrants were rescued," the coastguard statement added.

The Dogan news agency said all 11 victims, including five children, were Syrians.

Video broadcast by the DHA network showed half a dozen bodies laid out near ambulances after they had been recovered from the water.

Police said they arrested two people believed to be human smugglers who testified that they were on the boat with the refugees.

READ MORE: 2016 - The year the world stopped caring about refugees

The number of refugees caught crossing the Aegean Sea between Turkey and Greece has fallen by 85 percent since a refugee deal was signed with the European Union last year, according to data compiled from the Turkish coastguard command.

According to official figures, 16,627 refugees were intercepted in the Aegean after the Turkey-EU deal while this figure was 111,133 a year before the agreement.

The data shows that between April 2015 and March 2016, 437 people drowned while attempting to reach Greece. This figure fell by 95 percent to 20 since the deal was signed between Ankara and Brussels.

The agreement, however, largely shut down the eastern passage to Europe, making the more dangerous route from Libya to Italy the main departure point for people attempting to cross the Mediterranean Sea by boat to various parts of Europe.

The deaths in the Aegean came as aid workers on Friday said they feared about 250 people may have drowned in the Mediterranean after two partially submerged rubber dinghies were found off the coast of Libya.

More refugees died in the Mediterranean over the first nine weeks of 2017 compared to the same period in 2016, the International Organization for Migration (IOM) says. From January 1 to March 9 this year, at least 521 people drowned while attempting to cross the rough waters compared with 471 in the same period a year ago.

There were about 5,000 recorded deaths in all of 2016.