ATHENS — Greece’s coast guard on Monday prevented at least 590 migrants from illegally entering the country’s waters in the eastern Aegean Sea from neighboring Turkey in assorted vessels, authorities said.

A coast guard statement said the migrants were believed to have been aboard five sailing yachts and four inflatable dinghies that were spotted and turned back before reaching Greek waters in a series of separate incidents.

It said the larger vessels are believed to have been planning to sail past Greece to fellow European Union member Italy, following what has developed in recent years into a key smuggling route.

The statement said that Turkish authorities were notified to pick up the passengers on the vessels, as they had started off from Turkey’s shores. It said three of the yachts returned to the Turkish coast of their own volition, and all the other migrants were eventually taken back by Turkish patrol vessels.

Greece remains a major destination for people fleeing conflict or poverty who seek a better life in the EU. In recent years, stricter policing of Greece’s eastern sea border with longtime regional rival Turkey has drastically reduced the numbers, which had reached a record of about 1 million people in 2015.

Human rights groups and Turkish authorities have repeatedly accused Greek officials of illegally sending back to Turkey asylum-seekers who had already succeeded in entering Greece. Athens denies that.