Greece's coastguard said it was engaged in two separate rescue operations on Tuesday in search of dozens of migrants feared missing in gale-force winds.
A coastguard spokeswoman said nearly 60 people were believed to be missing near the island of Evia after their boat sank in winds of over 60 kilometres (37 miles) per hour.
A coastguard spokesman said Greece's high-seas patrol had rescued nine survivors -- Afghans, Egyptians and Iranians -- from an islet to the south of Evia island.
They "said there were 68 people in total on board the sailboat", spokesman Nikos Kokkalas told public television ERT.
A similar operation was underway near the island of Samos to find eight people believed to be missing since Monday.
Four migrants rescued said there were 12 people on board a dinghy that overturned.
Greece, Italy and Spain are destinations for people fleeing Africa and the Middle East in search of safety and better lives in the European Union.
The Greek coastguard has said it rescued about 1,500 people in the first eight months of the year, compared to fewer than 600 last year.
Greek officials say people smugglers now often take a longer and more perilous route south, sailing out from Lebanon instead of Turkey, to bypass EU patrols in the Aegean Sea, in a bid to reach Italy.