Turkish Coastguard stopped nearly 200 people trying to reach Greece on Saturday, underlining the challenge security forces face in convincing refugees contemplating the voyage that they will not be allowed to enter the EU.
A controversial European Union deal to return refugees who landed on the Greek islands in the last fortnight to Turkey is due to start on Monday.
A group of 118 Eritreans, Syrians, Iranians and Lebanese people were halted on Saturday as they headed to the Greek island of Chios from Cesme in Turkey in two dinghies, local media reported.
Another group of 63 were stopped as they attempted to travel to Greece's Lesbos from the Turkish coastal town of Dikili.
Turkey agreed last month to take back all refugees who crossed informally into Greece after March 20 in exchange for financial aid, visa-free travel for Turks and slightly accelerated bloc-membership talks.
Thousands of refugees are still attempting the dangerous sea crossing, although arrivals have slowed. More than 1,900 people have reached Greece so far this week despite poor weather conditions, and a total of 5,622 have been registered by Greek authorities since March 20.
The UN estimates the death toll in Syria, since the war started in 2011 to be at least 250,000 while the Syrian Centre for Policy Research on Feb 10 released a report saying that the death toll in Syria has reached 470,000.
Additionally some 350,000 refugees have sought asylum in European Union states since the war began in Syria in 2011.
More than 5 million others took refuge in neighbouring countries of Turkey, Lebanon, Iraq and Egypt, Turkey hosts the largest number with almost 3 million.