The statement said several vessels and two aircraft were searching for other potential survivors.
ITALY SHIPWRECK: COAST GUARD SAYS DOZENS DEAD AFTER MIGRANT CRAFT CRASHES OFF COAST
Towns sit above the cliffs of Santorini near the Aegean Sea, where an overloaded migrant boat capsized on March 1, 2023. Two of the migrants drowned while one remains missing. (Marcos del Mazo/LightRocket via Getty Images)
It said the migrants' plastic boat was detected by a thermal camera as it approached Kos, and a patrol vessel dispatched to investigate found an "overloaded polyester speedboat in dire straits, letting in water, which then capsized."
The nationalities of the migrants were not immediately known.
The boat sank off Kos' eastern coast, and is believed to have set off from the nearby Turkish coast. Thousands of migrants — mostly from the Middle East and Africa — try to reach the eastern Greek islands from Turkey every year, seeking a better life in the European Union.