The Coast Guard did not give further details, according to Reuters.
Greece is one of the European Union's main entry points for migrants and refugees fleeing poverty and conflict in the Middle East, Africa, and Asia.
More than 15,600 people have arrived in Greece this year, according to data from the United Nations refugee agency UNHCR, nearly 12,000 of them by sea.
In June, hundreds of people drowned in international waters off Greece after the fishing trawler they were traveling on capsized en route to Italy from Libya.
AMK/PR