Greek authorities say hundreds of people using small boats and dinghies have arrived over the past day on eastern Aegean islands near the Turkish coast, part of a surge of tens of thousands of migrants landing on Greek shores in recent months.

The coast guard said 457 people had been rescued from the sea in 12 separate cases off the islands of Lesbos, Chios, Kalymnos and Kos in 24 hours from Monday morning. Another 304 people had made their way ashore Monday to Lesbos' main port of Mytilene.

The U.N. refugee agency, UNHCR, said Greece had seen 48,000 refugee and migrant arrivals so far this year, the second-largest number in a European Union nation after Italy, where 54,000 people have crossed the Mediterranean Sea.