Edirne / Istanbul (dpa) - After the opening of its borders towards the EU announced by Turkey , more than 13,000 migrants have arrived at the border with Greece , according to the UN Organization for Migration (IOM) .

Thousands of migrants, including families with young children, spent a cold night here, IOM reported early Sunday morning.

Turkish Interior Minister Süleyman Soylu said Turkey had let more than 75,000 migrants cross the border towards the EU. By Sunday morning around 10:00 a.m. local time (8:00 a.m.CET), 76,358 migrants would have crossed the border via the province of Edirne, the minister said on Twitter . In the province of Edirne there are border crossings to Greece and Bulgaria . However, initially neither Sofia nor Athens reported the arrival of large numbers of migrants.

According to Sunday's Ministry of Migration in Athens, Greek police have so far prevented 9,600 migrants from crossing the border. The country also strengthened its units on the border.

IOM reported that its employees had observed at least 13,000 people along the 212 km long border between Turkey and Greece who had gathered in groups of up to 3,000 people at border crossings.

The EU border protection agency Frontex has set the alarm level for all EU borders to Turkey to "high" due to the increased influx of migrants. Greece has also asked for reinforcements, Frontex said on Sunday. Steps have already been taken to deploy additional officials and technical equipment.

Earlier, Turkish President Recep Tayyip Erdogan confirmed that Turkey was no longer holding refugees on their way to Europe and said that the border had been opened to migrants. Since Friday, numerous migrants in Turkey have been making their way to the border and trying to get into the EU. There were first clashes at border crossings to Greece on Saturday, in the course of which tear gas was also used against the advancing migrants.

Turkey has already taken in more than 3.6 million refugees from Syria . A refugee pact with the EU in 2016 actually stipulates that Turkey is preventing migrants from entering the EU. With this new position, Ankara is obviously trying to force more EU money to accommodate and care for the refugees.

EU Commission President Ursula von der Leyen and EU Council President Charles Michel are concerned about the situation on the EU's external borders with Turkey. "Our top priority is that Greece and Bulgaria have our full support," tweeted von der Leyen on Saturday evening. The EU is ready for further support, also with additional forces from the EU border protection agency Frontex.

In view of the escalation of the refugee situation on the EU border with Turkey, the Greens now see Chancellor Angela Merkel (CDU) as an obligation. "The Federal Government must now press as quickly as possible that there is a European solution for the distribution of refugees," Green Party leader Katrin Göring-Eckardt told the newspapers of the Funke media group (Sunday). If necessary, Merkel would have to forge an "alliance of the willing".

FDP General Secretary Linda Teuteberg called for completely different consequences in view of the reports on the opening of the borders by Turkey. "Payments to Turkey must be suspended immediately if President Erdogan breaks agreements," said Teuteberg of the "Bild am Sonntag". Merkel must now "put all its weight into play" so that a situation like 2015 does not repeat itself. In addition, she had to emphasize "that an uncontrolled migration to Germany is prevented by all means of the rule of law".

In the fighting in Syria, Turkey has killed more than 70 Syrian government soldiers and allied militias in the Syrian provinces of Idlib and

Alepo, according to activists. Initially, 45 regime soldiers were killed in attacks with combat aircraft, drones and artillery, and 26 other fighters in later attacks, the Syrian Observatory for Human Rights said on Saturday.

According to Erdogan, Turkey had launched several attacks in Syria. Equipment for the construction of chemical weapons as well as air defense systems and runways were destroyed, Erdogan said in Istanbul . The Syrian government denied the allegations and accused Erdogan of "misleading" statements and exaggeration. The background to the retaliation attacks is the death of numerous Turkish soldiers in Syria.