ATHENS — Riot police and the Greek army on Saturday deployed tear gas along the country’s land border with Turkey to try to stop migrants from entering the country.

A government spokesman said thousands of asylum seekers were attempting to cross along the heavily militarized border along the Evros river in northeastern Greece, after Turkey said it would no longer work to prevent migrants trying to reach Europe.

It marks a fresh escalation in the EU’s migrant crisis and is the first major test for Greece’s conservative New Democracy government since coming to power in July.

European Commission President Ursula von der Leyen said that the EU was following the situation “closely and with concern,” and was in contact with both Greek Prime Minister Kyriakos Mitsotakis and his Bulgarian counterpart, Boyko Borissov.

“Our top priority at this stage is to ensure that Greece and Bulgaria have our full support. We stand ready to provide additional support including through #Frontex on the land border,” she tweeted Saturday evening.

Austrian Chancellor Sebastian Kurz suggested Austria could consider closing its border if the situation worsens.

Greek authorities said they had intercepted around 4,000 people attempting to cross at points along the 50-mile border on Friday night. Some estimates suggested more than 1,000 made it to Greece on Friday, although the government denied these estimates. After 66 people were arrested Friday night, another 70 were arrested on Saturday. Officials said Saturday night more than 10,000 people were at the border.

Around 1,000 people were reported to be stranded between Turkey and Greece.

“Greek authorities [on Friday] faced an organized, massive and illegal attempt of border violation,” government spokesman Stelios Petsas said Saturday. “We will strengthen our forces on land and at sea ... The government is determined to do whatever it takes to protect our borders.”

Greek Foreign Minister Nikos Dendias on Saturday spoke by phone with the EU's High Representative for Foreign Affairs Josep Borrell and requested an extraordinary meeting of the EU’s Foreign Affairs Council.

In an interview, Dendias accused Turkey of breaching international law.

Turkish Foreign Minister Mevlüt Çavuşoğlu responded on Twitter: “Look who’s lecturing us on international law! They’re shamelessly throwing tear gas bombs on thousands of innocents piled at their gates. We don’t have an obligation to stop people leaving our country but Greece has the duty to treat them as human beings!”

Turkish President Recep Tayyip Erdoğan reiterated Saturday that the country no longer intended to work to prevent migrants from entering Europe. “We will not close these doors ... Why? The European Union needs to keep its promises. We don’t have to take care of this many refugees, to feed them,” he said.

Austrian Chancellor Sebastian Kurz suggested Austria could consider closing its border if the situation worsens.

Kurz tweeted Saturday that Austria is ready to provide additional police support to other countries but added, “If the protection of the EU's external border is unsuccessful, Austria will protect its borders.”

A statement by European Council President Charles Michel read: “The EU is actively engaged to uphold the EU-Turkey Statement and to support Greece and Bulgaria to protect the EU’s external borders.”

Greek authorities estimated thousands of migrants are also gathering along the Turkish coastline opposite the Greek islands waiting to cross the Aegean Sea. So far arrivals to the islands have been relatively low due to poor weather conditions, with about 140 people estimated to have landed throughout Friday and Saturday.