A four-year-old boy died on a boat crossing the Aegean Sea, the Greek coastguard said Wednesday, as the flow of refugees and migrants increased again after a brief drop in numbers.

The body of the boy, identified as Afghan by aid groups, was found in a boat that landed on the island of Chios, the coastguard said.

His family were among 600 migrants who arrived on the island on Wednesday, the day after the government inaugurated a registration facility to regulate the influx to Greece's eastern Aegean islands after over 800,000 people fleeing war and poverty landed there last year.

Similar facilities, known as hotspots, will operate on the islands of Lesbos, Leros, Samos and Kos at the insistence of the European Union, which wants to keep additional economic migrants out of the continent, and prevent possible extremists from sneaking in under the guise of refugees.

Lesbos gas seen another 1,076 people arrive since Tuesday, after Greek authorities said the flow had dropped from around 2,500 arrivals per day to 200.

"There has been a slight pick-up in arrivals," a coastguard source said.

Turkey is hosting 2.5 million refugees from Syria's civil war and hundreds of thousands from Iraq, and is increasingly bitter that it has been left to shoulder the burden.

A summit will be held in Brussels on Thursday between Turkey and eleven EU members to debate a German idea of flying refugees directly to Europe, and thereby reducing the number of deaths in the Aegean.

Over 300 people have already died in the crossing this year according to the International Organisation for Migration.