Turkish President Recep Tayyip Erdogan on Thursday threatened to send the millions of refugees in Turkey to EU member states, as NATO pledged to deploy ships to the Aegean Sea to ease the migrant crisis.

Erdogan stepped up his denunciations of Western policy on migrants in a speech in Ankara, confirming he had threatened EU leaders at a summit meeting in November that Turkey could say "goodbye" to the refugees.

Alarm is growing in EU capitals that thousands of migrants are still crossing the Aegean daily from Turkey after over a million made the perilous journey last year.

NATO has agreed to send a naval group to the Aegean to crack down on people-smugglers feeding the influx of migrants, while Greece is considering sending anyone picked up in the waters back to Turkey.

Turkey, already home to some three million refugees, is also under EU and UN pressure to take in tens of thousands of Syrian refugees fleeing regime advances in the Aleppo region.

Erdogan said Turkey had every right to turf the refugees out of the country if it so wished.

"We do not have the word 'idiot' written on our foreheads. We will be patient but we will do what we have to. Don't think that the planes and the buses are there for nothing," Erdogan said.

- 'Defended Turkey's rights' -

Greek website euro2day.gr had reported that Erdogan made the threat to EU Commission president Jean Claude Juncker in November, quoting him as saying: "We can open the doors to Greece and Bulgaria anytime and put the refugees on buses."

"I am proud of what I said. We have defended the rights of Turkey and the refugees. And we told them (the Europeans): 'Sorry, we will open the doors and say 'goodbye' to the migrants'," Erdogan said in his speech Thursday.

Turkey is already hosting 2.5 million refugees from Syria's civil war and hundreds of thousands from Iraq and is increasingly bitter it has been left to shoulder the burden.

The EU has agreed to give Ankara three billion euros ($3.3 billion) in financial aid for the refugees, but the funds have yet to be handed over two-and-a-half months after they were agreed.

Erdogan said Turkey had already spent some $9 billion on hosting refugees and lashed out at the UN for pressing it to let in tens of thousands of Syrians fleeing fighting in Aleppo massed on its border.

The NATO deployment follows a request this week by alliance members Germany, Greece and Turkey for assistance in tackling Europe's biggest migrant crisis since World War II.

According to the International Organization for Migration (IOM), by February 7, 70,365 migrants arrived by sea in Greece from Turkey, an average of 2,000 a day. It said 319 perished on the way.

- Send them back -

Among them was an eight-year-old girl, whose body was found by Turkish security forces Thursday washed up on the shore close to Didim in the Aydin region.

She had been dead for some 15 days, had no clothes and her body was starting to rot, the Radikal online daily said.

Secretary General Jens Stoltenberg said NATO is "now directing the standing maritime group to move into the Aegean without delay and start maritime surveillance activities".

"This is not about stopping and pushing back (refugee boats)... but about critical surveillance to help counter human trafficking and criminal networks."

The group comprises three ships that are currently under German command.

German Defence Minister Ursula Von der Leyen said "there is a clear accord with Turkey that any refugees picked up will be sent back to Turkey".

Greece, meanwhile, is also considering sending back migrants picked up in the Aegean Sea to Turkey.

A government source told AFP Athens is mulling whether to declare Turkey a "safe third country" which would allow it to return any asylum seekers picked up in the waters.

"No decision has yet been taken", but "it is being looked at", the source said, adding that while Greece might make the decision unilaterally, Turkey would have to agree to it to be put into practice.