ISTANBUL - Six children died early Friday when two boats carrying refugees to Greek islands capsized off Turkey's Aegean coast, the Turkish coast guard reported.

In one of the incidents, two siblings, aged 1 and 4, lost their lives when a boat with 23 refugees on board overturned amid stormy weather off the cost of Bodrum.

Another small boat carrying 55 Syrian and Afghan refugees to the Greek island of Lesbos sank off the coast of Canakkale, causing the death of four children. Turkish coast guard later found their bodies.

More than 3,000 refugees fleeing war-torn Syria have died on their way to Greek islands via Turkey, according to the International Organization for Migration.

Over 600,000 refugees have reportedly reached Greek islands so far this year, in a crisis that has alarmed the European Union (EU).

The EU and Turkish leaders are scheduled to hold a special summit on Sunday to finalize a deal on curbing the refugee influx from the Middle East to Europe.