European Commission President Ursula von der Leyen and other top EU officials are set to visit the Turkey-Greece land border on Tuesday.

The aim of the trip is to show solidarity with Greece and Prime Minister Kyriakos Mitsotakis. Thousands of migrants have arrived at crossing points after Turkey opened its borders last week.

"The challenge that Greece is facing right now is a European challenge," von der Leyen said.

The visit comes a day after a Syrian boy drowned off the Greek island of Lesbos. While most of the migrants survived after a boat capsized, the child died soon after being pulled from the sea.

It was the first fatality since restrictions were eased at the borders. 

Read more: Europe faces 'serious decision' on refugees amid Idlib catastrophe

Turkey is currently home to 3.7 million Syrian refugees. Nearly 1 million have fled fighting in the Idlib region since December.

In a telephone call with German Chancellor Angela Merkel on Monday, Turkish President Recep Tayipp Erdogan urged Europe to "share the burden."

"After we opened the doors, there were multiple calls saying, 'Close the doors,'" Erdogan said in a televised address to the nation. "I told them, 'It's done. It's finished. The doors are now open ... hundreds of thousands have crossed, soon it will be millions."

Merkel said even if Ankara "currently does not feel sufficiently supported" by Europe, " ... it is wholly unacceptable to then take this out on refugees."

Read more: Greece blocks 10,000 migrants at Turkish border

Greece calls it an 'invasion'

Greece said around 1,000 people had reached its eastern Aegean Islands. Development Minister Adonis Georgiadis called the migrant surge "an organized invasion from a foreign country."

"Turkey is making use of innocent people in its efforts to destabilize Greece and Europe," he told the Greek state television ERT TV.

The Greek Prime Minister spoke to US President Donald Trump about the border situation, his office said. Trump, it said, "recognized the right of Greece to enforce the law on its borders."

Read more: Refugee crisis in Greece: Anger and foreboding grow on Lesbos

Protests in Lesbos

In 2016, the EU and Ankara signed a deal that saw Turkey keep refugees in its territory in exchange for monetary support.

The move to open borders is seen as a bid to pressure Europe into supporting its military operation in Syria.

Last month, residents on the island of Lesbos protested against the plans for a new migrant center following violent clashes with riot police. On Sunday, locals refused to let migrants disembark from a dinghy that had just arrived.

With many shouting "Go back to Turkey," the residents stopped around 50 migrants, including children, from landing their boat after several hours at sea.

adi/rt (AP, Reuters)