A three-year-old refugee boy drowned early Saturday near the Greek island of Chios after the engine of the boat his group was sailing in exploded, the Greek coastguard said.
And police in Thessaloniki said a 5-year-old Syrian girl had been killed by a train on Friday whilst walking on the railway tracks near the town of Alexandroupolis.
Dozens of children have died as their families attempt to enter Europe from war-torn and impoverished countries this year, most of them in the Aegean Sea.
In the Chios incident, the explosion threw the boat occupants into the water as it lay immobilised in shallows east of the island, the coastguard said.
Fifteen other people were rescued, including two that required hospitalisation, it said.
An 18-year-old was arrested as a suspected trafficker.
Greece has been overwhelmed this year by a migration crisis unseen in Europe since World War II.
The United Nations on Friday said over 800,000 people have crossed the Mediterranean to Europe this year, with over 3,400 dying in the process.
Greek Prime Minister Alexis Tsipras will travel to Turkey next week to press the country’s leaders to take a stronger stance against refugee traffickers.