The NATO ships will collect information and conduct reconnaissance on human traffickers using rickety boats to bring migrants to Europe.

The information will then be forwarded to Turkish and Greek authorities as well as the EU border protection agency Frontex.

The EU and Turkey hope that the NATO mission will discourage human traffickers and migrants from making the dangerous journey across the Aegean.

The mission gets underway as EU leaders reached an outline agreement with Turkey to resolve the migrant crisis:

NATO has emphasized the mission is not meant to stop or push back migrants at sea. The goal is to provide information for Turkish, Greek and EU authorities, who will then respond to migrant boats.

NATO is only authorized to intervene if a migrant boat is in distress. In such a case the boat's occupants will be taken back by Turkey.

Since NATO members approved the plan last month, the ships belonging to the Alliance's standing naval group, a permanent reaction force deployed in the Mediterranean, have been in international waters in the Aegean.

Tens of thousands of refugees have crossed by boat from Turkey to Lesbos.

A long-running maritime dispute between Greece and Turkey had slowed down deployment in the two country's territorial waters.

Germany is leading the mission supported by ships from Canada, Turkey and Greece. Britain, France and the Netherlands have also said they would commit ships.

Germany's Defense Ministry said on Monday the naval group's flagship, the German combat support ship "Bonn" (pictured) had moved into the narrow territorial waters separating Turkey and the Greek island of Lesbos.

cw/jil (dpa, Reuters)