ATHENS - Leaders of European Union (EU) institutions expressed on Tuesday their support for Greece and determination for a common European response to the refugee, migrant challenge after a visit to the Greek-Turkish land border.

European Council President Charles Michel, European Commission President Ursula von der Leyen, European Parliament President David Sassoli, and Croatian Prime Minister Andrej Plenkovic attended the press conference held in the town of Kastanies in the Evros region with Greek Prime Minister Kyriakos Mitsotakis, after being briefed on the crisis unfolding on the Greek-Turkish land border since last Friday.

Tens of thousands of refugees and migrants have gathered on the Turkish side of the border, after Ankara said it could no longer prevent them from reaching Europe's borders.

Greek police and armed forces have been strengthened on the border and until Monday evening they had prevented over 24,000 illegal crossings and detained 183 persons who crossed the border, according to Greek government sources.

In the past few days, the Greek government has repeatedly stated that it faces a national security threat and therefore has stepped up patrols on land and sea borders and requested the immediate substantial aid from other EU member states.

"The Greek borders are the European borders and what you are doing is important for Greece and crucial as well for the future of the EU. We are together, because we consider borders protection is essential," Charles Michel said on Tuesday.

"We have come here today to send a very clear statement of European solidarity and support to Greece," von der Leyen stated.

Greece will receive an additional 700 million euros ($784 million) of financial aid for the management of the crisis, she announced, noting that European Border and Coast Guard Agency (Frontex) is already getting ready to deploy a rapid border intervention unit to assist Greece in dealing with the situation.

"It is the responsibility of Europe as a whole and we will manage it in an orderly way, with unity, solidarity and determination. Those who seek to test European unity will be disappointed," she added.

"Turkey is not an enemy and people are not just means to reach a goal," she stressed, expressing her compassion for people who reached Europe's borders on false promises, as she noted.

Sassoli, on his part, highlighted the need for a strong common European approach on the issue which is on the table for the past five years, since the first mass flows started to cross the Aegean Sea.

Over one million reached Greece since 2015, fleeing wars and extreme poverty and continued their journey to other European countries until the closure of borders along the Balkan route in the winter of 2016 and the signing of EU-Turkey agreement aimed to stem the influx.

Under the deal, Turkey would be provided with financial assistance to accommodate the millions of refugees and migrants hosted in the country in return for increased efforts to deal with the human smuggling networks operating in the region.

"We need - we see it every day - to strengthen our common policy framework to deal with migration on a European level. We are here today for one more reason, to tell Turkey that we do not want more talks, but that Turkey respects what has been agreed," Sassoli said on Tuesday.

Stressing that nobody wishes to see a replay of the 2015-2016 refugee crisis, Plenkovic also voiced support for Greece, calling for determination to give a European response to the new challenge.

"Greece is now the shield of the external borders of the EU... We will send a message to Turkey that good relations between Turkey and the EU depend on both of us. We will seek to find political and diplomatic solution to deescalate the situation we have today here," the Croatian prime minister told the press briefing.

Greece has demonstrated solidarity to people in need for years and is currently hosting about 100,000 already, but cannot shoulder alone all the burden of safeguarding Europe's borders from more massive flows, said Greek prime minister.

"Greece expects tangible solidarity from the EU and I can tell you that the presence of the entire leadership of the EU here at the outer border of Europe sends a clear signal to everyone. But let's be honest. Europe has not been up to the task of dealing with the migrant crisis. I hope this crisis will serve as a wakeup call for everyone to assume their responsibilities," Mitsotakis stated.

"We stand ready to support Turkey in dealing with its refugee problem and find a solution to the Syria conundrum, but not under these circumstances... Migrants and refugees cannot be used as instruments, as pawns in a geopolitical game," the Greek leader concluded. (1 euro= $1.12)