Two children are among at least 16 refugees who have drowned attempting to cross from Turkey to Greece.

The sole survivors of the disaster were two women – one of them pregnant – who said around 25 people had been loaded on to a smugglers’ boat towards the island of Lesbos.

The UN Refugee Agency (UNHCR) said a six-year-old boy was found dead in Greek waters, alongside six women and two men.

Seven more bodies, of six men and a child were found in Turkish waters by the coastguard following the sinking on Monday night.

A spokesperson said that the survivors, an eight-month pregnant woman from the Democratic Republic of the Congo and another woman from Cameroon, were “out of danger” following hospital treatment and would receive accommodation and support in Greece.

“The number of people crossing the Aegean to Greece has dropped drastically over the past year, but this tragic incident shows that the dangers and the risk of losing one’s life remains very real,” said Philippe Leclerc, a regional representative of the UNHCR.

Refugee crisis: Stranded refugees face deteriorating conditions in Greece camps

It was the second reported boat disaster in waters between Turkey and Greece this year, which has seen a record number of refugees die attempting the longer and more treacherous crossing from Libya to Italy.

It has become the dominant sea route to Europe after new regulations were imposed under the controversial EU-Turkey deal in March 2016, seeing anyone arriving on Greek islands detained under the threat of deportation.

More than 62,000 asylum seekers have been stranded in Greece by the agreement and border closures throughout Europe, despite warnings over a “growing epidemic” of sexual violence and exploitation and suicide attempts in refugee camps.

Around 4,900 migrants have made the voyage this year, according to UNHCR data – an average of 20 a day – far down on the total of 173,000 for 2016.

Many of those already in Greek camps have been waiting for their asylum claims to be processed for up to a year while living in dire conditions under the threat of violent protests and attacks by right-wing groups.

A group of 12 Syrians of Kurdish origin started a hunger strike on Friday at the notorious Moria detention camp on the island of Lesbos.

Refugee crisis - in pictures Show all 27 1 /27 Refugee crisis - in pictures Refugee crisis - in pictures A child looks through the fence at the Moria detention camp for migrants and refugees at the island of Lesbos on May 24, 2016. AFP/Getty Images Refugee crisis - in pictures Ahmad Zarour, 32, from Syria, reacts after his rescue by MOAS (Migrant Offshore Aid Station) while attempting to reach the Greek island of Agathonisi, Dodecanese, southeastern Agean Sea Refugee crisis - in pictures Syrian migrants holding life vests gather onto a pebble beach in the Yesil liman district of Canakkale, northwestern Turkey, after being stopped by Turkish police in their attempt to reach the Greek island of Lesbos on 29 January 2016. Getty Images Refugee crisis - in pictures Refugees flash the 'V for victory' sign during a demonstration as they block the Greek-Macedonian border Refugee crisis - in pictures Migrants have been braving sub zero temperatures as they cross the border from Macedonia into Serbia. Refugee crisis - in pictures A sinking boat is seen behind a Turkish gendarme off the coast of Canakkale's Bademli district on January 30, 2016. At least 33 migrants drowned on January 30 when their boat sank in the Aegean Sea while trying to cross from Turkey to Greece. Getty Images Refugee crisis - in pictures A general view of a shelter for migrants inside a hangar of the former Tempelhof airport in Berlin, Germany Refugee crisis - in pictures Refugees protest behind a fence against restrictions limiting passage at the Greek-Macedonian border, near Gevgelija. Since last week, Macedonia has restricted passage to northern Europe to only Syrians, Iraqis and Afghans who are considered war refugees. All other nationalities are deemed economic migrants and told to turn back. Macedonia has finished building a fence on its frontier with Greece becoming the latest country in Europe to build a border barrier aimed at checking the flow of refugees Refugee crisis - in pictures A father and his child wait after being caught by Turkish gendarme on 27 January 2016 at Canakkale's Kucukkuyu district Refugee crisis - in pictures Migrants make hand signals as they arrive into the southern Spanish port of Malaga on 27 January, 2016 after an inflatable boat carrying 55 Africans, seven of them women and six chidren, was rescued by the Spanish coast guard off the Spanish coast. Refugee crisis - in pictures A refugee holds two children as dozens arrive on an overcrowded boat on the Greek island of Lesbos Refugee crisis - in pictures A child, covered by emergency blankets, reacts as she arrives, with other refugees and migrants, on the Greek island of Lesbos, At least five migrants including three children, died after four boats sank between Turkey and Greece, as rescue workers searched the sea for dozens more, the Greek coastguard said Refugee crisis - in pictures Migrants wait under outside the Moria registration camp on the Lesbos. Over 400,000 people have landed on Greek islands from neighbouring Turkey since the beginning of the year Refugee crisis - in pictures The bodies of Christian refugees are buried separately from Muslim refugees at the Agios Panteleimonas cemetery in Mytilene, Lesbos Refugee crisis - in pictures Macedonian police officers control a crowd of refugees as they prepare to enter a camp after crossing the Greek border into Macedonia near Gevgelija Getty Images Refugee crisis - in pictures A refugee tries to force the entry to a camp as Macedonian police officers control a crowd after crossing the Greek border into Macedonia near Gevgelija Getty Images Refugee crisis - in pictures Refugees are seen aboard a Turkish fishing boat as they arrive on the Greek island of Lesbos after crossing a part of the Aegean Sea from the Turkish coast to Lesbos Reuters Refugee crisis - in pictures An elderly woman sings a lullaby to baby on a beach after arriving with other refugees on the Greek island of Lesbos after crossing the Aegean sea from Turkey Getty Images Refugee crisis - in pictures A man collapses as refugees make land from an overloaded rubber dinghy after crossing the Aegean see from Turkey, at the island of Lesbos EPA Refugee crisis - in pictures A girl reacts as refugees arrive by boat on the Greek island of Lesbos after crossing the Aegean sea from Turkey Getty Images Refugee crisis - in pictures Refugees make a show of hands as they queue after crossing the Greek border into Macedonia near Gevgelija Getty Images Refugee crisis - in pictures People help a wheelchair user board a train with others, heading towards Serbia, at the transit camp for refugees near the southern Macedonian town of Gevgelija AP Refugee crisis - in pictures Refugees board a train, after crossing the Greek-Macedonian border, near Gevgelija. Macedonia is a key transit country in the Balkans migration route into the EU, with thousands of asylum seekers - many of them from Syria, Afghanistan, Iraq and Somalia - entering the country every day Getty Images Refugee crisis - in pictures An aerial picture shows the "New Jungle" refugee camp where some 3,500 people live while they attempt to enter Britain, near the port of Calais, northern France Getty Images Refugee crisis - in pictures A Syrian girl reacts as she helped by a volunteer upon her arrival from Turkey on the Greek island of Lesbos, after having crossed the Aegean Sea EPA Refugee crisis - in pictures Refugees arrive by boat on the Greek island of Lesbos after crossing the Aegean sea from Turkey Getty Images Refugee crisis - in pictures Beds ready for use for migrants and refugees are prepared at a processing center on January 27, 2016 in Passau, Germany. The flow of migrants arriving in Passau has dropped to between 500 and 1,000 per day, down significantly from last November, when in the same region up to 6,000 migrants were arriving daily.

The UNHCR said its staff were working to help resolve the situation amid concern for their health, with the strikers cutting out water on Sunday.

They are preparing a letter to Greek authorities demanding their claims be considered in line with international law and the 1951 Refugee Convention.

The worsening situation is driving migrants into the hands of smugglers in desperation to escape the country.

An Iranian man died near the north-eastern city of Xanthi on Monday night after a van carrying him and 13 other migrants crashed while being chased by police.

Police said the van's driver, a suspected smuggler from Moldova, had swerved past a motorway checkpoint and crashed on a rural road before being arrested.

Refugees have died in fires and of hypothermia and suffocation in Greek camps, where some are on hunger strike (AFP/Getty)

The migrants found inside, from Bangladesh, Pakistan, Iraq, and Iran, are believed to have crossed from neighbouring Turkey over a river that separates the two countries.

Almost 1,100 asylum seekers have died in attempted sea journeys to Europe so far in 2017, while several more have been killed by hypothermia, suffocation or in accidents on land.

Despite the record deaths, humanitarian organisations carrying out search and rescue operations have been increasingly attacked for allegedly aiding smugglers, which they deny.

Sophie Beau, the co-founder of rescue charity SOS Mediterranee, said NGOs were being forced to act by the “failure of European states”, who should be increasing rescue capacity themselves.

“NGOs are being blamed for our presence, when authorities should be blamed for their absence,” she added.

“There’s a humanitarian tragedy unfolding in front of our eyes at the door of Europe and we cannot just remain blind.”