At least 12 migrants including four children have died after their inflatable boat sank off a western Greek island in the Ionian Sea, port authorities say.

The Greek Merchant Marine Ministry said the incident occurred early Friday, off the coast of Lefkada, an island in the Ionian Sea, and the migrants were presumed to have been headed to nearby Italy.

"A search is under way for other victims," a spokeswoman for the port police told AFP, adding that the migrants were travelling in an eight-metre (26-foot) inflatable dinghy that was found in the area.

The survivors landed at Paleros, a small western Greek coastal town opposite Lefkada. Their nationalities and port of departure were not immediately known.

"We find it puzzling how this accident occurred as weather conditions in the area were excellent this morning, and it also happened near the coast," Costas Aravanis, Lefkada's mayor, told Skai TV.

Aravanis said coast guard boats and divers had searched in the Palairos area, between Lefkada and the mainland, before the effort was eventually called off about four hours after the sinking was first reported.