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 lull.

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 Athens inaugurated a registration facility there to regulate the huge influx of people fleeing war and poverty.

Greece, which saw more than 800,000 people land on its Aegean islands last year, has faced EU criticism over its handling of the crisis.

Over 300 people have already died this year trying to make the short but perilous crossing from Turkey to Greece, according to the International Organization for Migration.

Migrant centres known as hotspots will operate on the islands of Lesbos, Leros, Samos and Kos as well as Chios.

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

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

Neighbouring Turkey is hosting more than 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 11 EU members to debate a German idea of flying refugees directly to Europe, and thereby reducing the number of deaths in the Aegean.

Greece's justice ministry said on Wednesday it was creating an upgraded coroner's office on Lesbos, which receives the bulk of Aegean arrivals and also records the most deaths.

Until now, a sole coroner Theodoros Noussias, had been left to handle the task.

Noussias ran out of space at the morgue and had to make do with a refrigerated container donated by a British aid group to house bodies.

‘It is such a pity that so many people drown -- especially the children,’ he said.