Some 40 per cent of the refugees stranded at the camp Moria on Lesbos are children, a worker from aid organization Doctors Without Borders (MSF) told radio Athina984 on Tuesday.

Of the more than 2,000 children sheltered in the overcrowded camp, 432 are unaccompanied minors, Apostolos Veizis, the MSF medical supervisor for Greece said.

"In the field hospitals we run there, 52 per cent of the patients are children under the age of five," he said.

In addition to children, in the camp are many pregnant women and some 500 people on a waiting list for psychiatric care.

Veizis faults a lack of political will hindering the resolution of the issue of stranded people, claiming that the EU-Turkey deal on refugees and migrants trapped all sides instead of solving the problem.

Brussels and Ankara agreed in 2016 to stem the flow of people fleeing into the European Union across the Aegean and the Balkans.

The deal reduced the inflow to a trickle, but it also stranded all those arriving on the Aegean islands, where they have to apply for asylum and remain during processing.

With the applicants processed very slowly and new people arriving, the refugee camps on the islands have become overcrowded, with 5,500 people in the Moria camp, which was designed to hold only 2,330.