European Union leaders faced stern warnings at Thursday's summit meeting their credibility would suffer if they failed to respect pledges on tackling the refugee emergency.

The leaders promised last month to provide hundreds of millions of euros for Syrian refugees and to help Africa better manage its borders, as well as funding experts to fingerprint and screen new arrivals in Italy and Greece.

European Commission President Jean-Claude Juncker said he was still waiting and insisted "the member states have got to do what they promised to do."

"It's a question of credibility," he said.

The European Commission complained Wednesday that only three of 28 nations have pledged a total of just 12 million euros ($13.7 million) to a fund to help African nations better manage their borders. The pot is meant to total 1.8 billion euros (about $2 billion) over two years.

The EU's border agency and asylum office have appealed for a total of around 1,000 officers to help fingerprint people and decide whether they are eligible for asylum. So far, about a dozen of the 28 EU nations have offered around 130 personnel.

"We can, and must, do much better," said EU President Donald Tusk.

Meanwhile, away from the marbled EU headquarters in Brussels, the plight of migrants continuing to travel north up the continued remained dire.

Greece's coast guard was searching for eight people missing after a boat carrying people attempting to reach the eastern Aegean island of Lesbos off Turkey collided with a patrol boat and sank during a rescue operation. The coast guard said 31 people were rescued. The coast guard said it has rescued 830 people between Wednesday morning and Thursday morning off eastern Aegean islands.

It all pointed to the significant role of Turkey in the crisis.

German Chancellor Angela Merkel told the German parliament before her Brussels departure that "without doubt Turkey plays a key role in this matter. Because with more than 2 million refugees it currently bears the main burden of the flight from Syria."

The EU has offered Turkey 1.8 billion euros to help deal with the refugee challenge and is looking at easing visa restrictions for Turkish citizens.

President Recep Tayyip Erdogan wants European backing for a no-fly zone and safe area in northern Syria, and for Turkey's EU membership talks to be accelerated.

Senior EU officials are currently in Turkey trying to reach an agreement on the way ahead, and Juncker said the discussions "are going in the right direction."

More than 500,000 people fleeing war or poverty have entered Europe this year, most of them via Greece and Italy, overwhelming border authorities and reception facilities. Under the media spotlight, EU leaders pledged last month to provide hundreds of millions of euros in aid for Syrian refugees and to tackle the problem at its roots, in Africa and Turkey.