Thousands of child refugees and migrants entering Greece are at risk of exploitation and disease as local authorities are overwhelmed by the wave of immigration, an international charity said Wednesday.

Save the Children said that children are still living in "appalling conditions" in reception centers, where food, water, medicine and a safe place to sleep are in poor supply.

At least 110,000 people, mostly refugees from Syria and other war zones, but also economic migrants, have reached Greece's Aegean Sea islands from neighboring Turkey this year — a 400 percent increase over 2014.

Total arrivals could reach 200,000 by the end of the year, as desperation drives migrants to risk the perilous sea crossing in crammed, unseaworthy craft provided at high cost by smuggling gangs.

The influx has far exceeded the capacity of Greek authorities — who are struggling with the country's worst financial crisis in decades — to provide adequate reception and assistance. Most of the migrants see Greece as a stepping stone to more affluent European countries, and try to continue their journey north through the Balkans.

Save the Children said 4,270 children landed on the Greek islands in June alone.

"Vulnerable children, particularly those sleeping outside alone or locked in large mixed groups in cramped detention centers, are at risk of trafficking, sexual exploitation and physical abuse," the organization said in a report.

It added that children told Save the Children staff in the Aegean islands of Lesbos, Chios and Kos, and in the capital, Athens, that they hadn't eaten for days in some cases and were afraid to sleep outside or go to the bathroom at night because of the risk of abuse.

The report said babies and young children are particularly at risk from diarrhea, severe sunburn, heatstroke and dehydration. It appealed for European Union help to address the crisis.