Istanbul, March 1 (IANS): Turkish President Recep Tayyip Erdogan has said that 18,000 migrants have crossed his country's borders into Europe after Ankara "opened the doors" for them to travel, it was reported.

Turkey is hosting 3.7 million Syrian refugees, as well as migrants from other countries such as Afghanistan. It had previously stopped them from leaving for Europe under an aid-linked deal with the European Union (EU), the BBC reported.

But Erdogan accused the EU of breaking promises.

"We said months ago that if it goes on like this, we will have to open the doors. They did not believe us, but we opened the doors yesterday (Friday)," the BBC quoted Erdogan as saying here on Saturday.

He said that some 18,000 refugees had "pressed on the gates and crossed" into Europe by Saturday morning.

The number was expected to hit 25,000 to 30,000 in the coming days, he said but did not provide any evidence to support the figures.

"We will not close these doors in the coming period and this will continue. Why? The EU needs to keep its promises. We don't have to take care of this many refugees, to feed them," he said.

Meanwhile, the Greek government said that it had averted more than 4,000 attempts to cross into the country.

"The government will do whatever it takes to protect its borders," the BBC quoted government spokesman Stelios Petsas as saying on Saturday.

There were further clashes between migrants and Greek police on Saturday.

Greek authorities fired tear gas to attempt to disperse the crowds.