Fishermen in the Didim district of Aydın province in Turkey's Aegean region informed the Turkish Coast Guard of the dead refugees upon noticing their bodies floating on the water. The Turkish Coast Guard removed the five bodies from the water and rescued one migrant, who was reported to be in good condition.
The rescued refugees said there were another 16 refugees on the boat.
The Turkish Coast Guard has begun search and rescue operations to locate the other refugees.
Meanwhile, some 28 refugees and 12 human smugglers were caught during two different police operations in the Ayvalık district in the Aegean province of Balıkesir.
A motorboat and eight vehicles including two taxis owned by smugglers were seized during the operations by district police's anti-smuggling and organized crime teams.
The group of smugglers was attempting to transport refigees to the Greek island of Lesbos through Turkey's Cunda Island. Suspects, who were said to be from Istanbul, Şırnak, Balıkesir and Ayvalık, were sent to court, while 10 of them were arrested.
Since the beginning of 2016, some 24 smugglers have been arrested, according to local reports.