Greece calls EU talks as migrant numbers grow

"The number of migrants moving ... towards the border grew through the day as cars, taxis, and buses arrived from Istanbul," IOM's Turkey chief Lado Gvilava said.

"Most of those on the move are men but we are also seeing many family groups traveling with young children," Gvilava added.

For his part, Turkish president Recep Tayyip Erdogan said 18,000 people had crossed to Greece on Saturday and that the number would soon grow to 30,000.

Turkish interior minister Suleyman Soylu said on Sunday that 76,000 people were on the way to Greece.

The new crisis came after Syrian forces killed 34 Turkish soldiers in northwest Syria last week, prompting Erdogan to launch a counter-offensive and to say his 2016 deal with the EU to keep refugees from coming was no longer valid.

Greece reacted by sending its army and navy to the border and by forbidding new asylum applications.

It said it had stopped almost 10,000 illegal crossings on Saturday and its foreign minister, Nikos Dendias, called for an emergency meeting of his EU peers, which is to be held later this week.

"The borders of Greece are the external borders of Europe. We will protect them. I will be visiting the Evros land border with Turkey along with [EU Council president] Charles Michel on Tuesday," Greek prime minister Kyriakos Mitsotakis said on Twitter.

"Once more, do not attempt to enter Greece illegally - you will be turned back," he added.

"Greece was the target of an organised, mass illegal attempt to violate its borders and has withstood it," Greek government spokesman Stelios Petsas said.

Bulgaria and Greece have also said they were boosting border security.

"Hungary must strengthen the protection of its borders and pay special attention to developments on the Balkan migration route," the Hungarian government said on Friday.

The EU foreign service, its border control agency, and individual EU leaders voiced support.

"The EU-Turkey Statement [migrant deal] needs to be upheld. The EU is engaged in supporting Greece and Bulgaria in addressing the unfolding situation," EU foreign affairs chief Josep Borrell said.

"We are redeploying equipment and additional officers to Greece," Frontex, the EU border control agency, said.

"A situation like 2015 must never be repeated," Austrian chancellor Sebastian Kurz also said, recalling a year in which more than 1m refugees, most of them from Syria, came to Europe.

"Austria is also ready to support the countries on the external border with additional police officers," Kurz added.

But "if the protection of the EU's external border is unsuccessful, Austria will protect its borders," he said, raising the spectre of internal EU border closures, as happened five years ago.

Fighting continues

At the same time, fighting continued in northwest Syria, increasing the chances that more people will come.

Turkey said it had killed 26 Syrian regime soldiers, shot down planes, and destroyed air defences using swarms of armed drones as well as rocket artillery in recent days.

Russia has fought alongside the Syrian regime for years, amid concern that Nato member Turkey and Russia could accidentally come to blows.

Erdogan said Russia ought to stand back so he could "do what is necessary" in military terms.

But French president Emmanuel Macron urged Turkey and Russia - the two main foreign powers in Syria - to return to a ceasefire instead.

"The president of the [French] republic stressed that an immediate cease to hostilities was needed and called on Russia and Turkey to establish a durable and verifiable ceasefire," Macron's office said on Friday.

"Over the past days, I have been in contact with key actors. I have called for an immediate de-escalation and for a lasting ceasefire, deplored the loss of lives," the EU's Borrell also said.

"There is only a political solution to this crisis," Borrell said.