Greece's coast guard says it has rescued 830 people in 20 search and rescue operations between Wednesday morning and Thursday morning off eastern Aegean islands.

The rescues, which occurred near the islands of Lesbos, Chios, Samos, Agathonissi and Kos, do not account for those who reach the shores themselves, generally in overcrowded inflatable dinghies.

On Wednesday, authorities recovered the bodies of a woman, a young girl and an infant from an overturned dinghy spotted by a helicopter of the European Union border policing agency Frontex. The recovery came after an all-day search following the rescue in nearby Turkish waters of 21 others who had been in the dinghy.

Hundreds of thousands of people fleeing war and poverty in their homelands have crossed illegally from Turkey to Greece this year.

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German Chancellor Angela Merkel says Europe must cooperate with Turkey in order to tackle the migrant crisis.

Merkel says that by improving conditions in those regions where migrants come from they may be dissuaded from traveling to Europe.

She told German lawmakers Thursday that "without doubt Turkey plays a key role in this matter" because it hosts almost 2 million Syrians and is a key transit point for migrants coming to Europe.

Merkel, who travels to Istanbul on Sunday, says talks with Turkish leaders won't tie cooperation on the refugee issue to the country's future membership of the European Union.