Two children were found unconscious after a vessel overturned at 0630 GMT in the Aegean Sea, Greek police said. One of them, a small boy, could not be revived, while the other was taken to hospital.
A child has died and another was hospitalised after a makeshift boat packed with dozens of migrants and refugees capsized off the coast of Lesvos en route from Turkey, Greek port police said.
Two children were found unconscious after the vessel overturned at around 08:30 am local time (0630 GMT) in the Aegean Sea, a spokeswoman said. One of them, a small boy, could not be revived, while the other was taken to the hospital.
A further "46 people are safe" following the accident, the official said.
Thousands more asylum seekers were trying to find a way across Turkey's western border with Greece Monday, with only dozens managing to pass through either border fences or fording the river there, after Turkey opened its side of the frontier to migrants and refugees to leave the country for Europe.
Greek police made use of tear gas against the crowds trying to push through. Holding white flags, the crowd of several hundred shouted “peace, peace,” asking to be let through into Greece.
Turkey declared its borders open to pressure the European Union into helping it handle the fallout from the war in neighbouring Syria.
Turkey launched Operation Spring Shield and is supporting the last of the opposition and rebel forces in the northwestern province of Idlib against the onslaught of Russian-backed Syrian regime forces.
Greek police fire tear gas on asylum seekers
Greek police fired tear gas to repel hundreds of asylum seekers who are trying to cross the border from Turkey on Sunday, with thousands more behind them.
Refugees and migrants responded to being fired at with tear gas by throwing stones at Greek police.
The Greek government called the confrontations a threat to national security.
“Do not attempt to enter Greece illegally – you will be turned back,” Prime Minister Kyriakos Mitsotakis said on Twitter after a security meeting on the situation.
It was the second straight day of clashes at the border crossing near the northeastern Greek town of Kastanies.
Turkey said on Thursday it would let asylum seekers cross its borders into Europe, despite a commitment to hold them in its territory under a 2016 deal with the European Union.
Ankara's move also comes after the European Union ignored Turkey's pleas for support in tackling the refugee crisis from Syria’s civil war.
Ankara has dismissed Greek criticism of its decision to open the border and has condemned Greece’s response to the migrants and refugees.
Rush to Greek border
At least 600 people had arrived by sea on the Greek islands of Lesvos, Chios and Samos close to the Turkish coast within a few hours on Sunday morning, police said.
Along the northeastern mainland border, some asylum seekers waded across a shallow section of the Evro River to the Greek side. Witnesses said there were groups of up to 30, including an Afghan mother with a five-day-old infant, by the side of a road after having forded the river.
The clashes occurred later in the day at the Kastanies crossing after riot police reinforced security there. No further details were immediately available as police were escorting reporters away from the scene, citing safety considerations.
The EU scrambled to respond to the new migrant crisis.
Officials at EU headquarters in Brussels called for emergency meetings of migration and foreign ministers to decide next steps, while EU border agency Frontex said it was in talks with Greece to help it guard the bloc’s external frontier.
German Chancellor Angela Merkel had a phone call with Boyko Borissov, the prime minister of Bulgaria, which also shares a border with Turkey, and agreed for the need for talks with Ankara, a German government spokesman said.
The Greek Prime Minister said he and European Council head Charles Michel would visit the Evros land border with Turkey on Tuesday.
'The borders are shut'
The crisis poses the toughest test for Greece since 2015 when it came precariously close to bailing out of the euro zone, and also brings into focus longstanding tensions with Turkey.
An automated text message sent to mobile phones in the northern border areas of Greece said the country had increased its security to a maximum, urging people not to attempt to enter.
Greece’s Skai TV said Greeks were using loudspeakers in the Kastanies border area to tell asylum seekers, in English and Arabic, that they were not welcome: “The Borders are Shut!”
Greece was the main gateway for hundreds of thousands of asylum seekers into Europe in 2015-16. More than 40,000 asylum seekers are stuck on the Aegean islands, living in severely overcrowded camps and filthy conditions.
A Greek government source put the number of people gathered on the Turkish side of the border on Sunday at 3,000, while the International Organization for Migration (IOM) estimated the number at 13,000.
On the island of Lesvos, a small group of Greeks attempted to prevent a dinghy full of migrants from coming in to berth at a harbour. “Go back to Turkey” a group of hooded individuals shouted.
Last week, there were clashes on Lesvos between riot police and locals protesting over a plan to create closed detention centres to house the migrant population.
Local residents say the islands are carrying a disproportionate burden.