Latest tragedies come amid increased number of crossings as people try to reach Europe before winter and a possible crackdown on arrivals
At least 22 people have drowned in the Aegean Sea after two boats sank, raising the death toll in the area over the past three days to nearly 50.
Thousands of Middle Eastern refugees and economic migrants have been seeking to reach the Greek islands in rough seas.
The Merchant Marine Ministry said 19 people were killed and 138 were rescued near the eastern island of Kalymnos, in one of the worst accidents in Greek waters since the mass migrant flows started after the war in Syria.
Four coastguard patrol vessels, a helicopter and three fishing boats helped rescue the survivors, and nobody was listed as missing, the ministry said. The accident occurred shortly before midnight on Thursday, when the wooden boat in which the migrants had left from Turkey took on water and sank in moderately strong winds.
At least three more people died when another migrant boat sunk off the nearby island of Rhodes. Three people are still missing, while six were saved.
Meanwhile, authorities on Friday raised to 16 the number of deaths from another migrant ship sinking off the island of Lesbos on Wednesday. They said 274 people have been rescued in total, while one more migrant remains listed as missing.
Lesbos has borne the brunt of the refugee crisis in Greece, with more than 300,000 people reaching the island this year on small boats from Turkey, police say. More than a third have come in October alone.
Greece is the main point of entry for people fleeing war and poverty in the Middle East and Africa, seeking a better life in Europe. More than half a million people, mainly Syrians and Afghans, have arrived so far this year from the nearby Turkish coast, rushing to avoid deteriorating weather conditions as winter approaches, as European governments consider taking tougher measures to try to limit the number of arrivals in Europe.