Turkey's Prime Minister Ahmet Davutoglu has told German Chancellor Angela Merkel and top EU officials that gaining visa-free travel for Turkish citizens was "vital" to the success of a crucial migrant deal.

"The issue of the visa waiver is vital for Turkey," he said at a joint press conference with Chancellor Merkel, European Council head Donald Tusk and European Commission Vice President Frans Timmermans.

Also speaking at the press conference European Council head Donald Tusk heaped high praise on Turkey for its reception of Syrian refugees, saying the country served as "the best example" in the world on caring for those fleeing war.

"Today Turkey is the best example for the whole world (on) how we should treat refugees," he said.

"This is not only a political and formal assessment... this is also my very private and personal feeling," he said.

Earlier today Chancellor Merkel, Mr Tusk and Mr Timmermans travelled to a refugee camp in Nizip, near the Syrian border, where they were expected to speak to some of the 5,000 or so people forced to flee their conflict-wracked country.

They were also expected to visit a child protection centre.

The trip comes a month after a deal on 20 March between the EU and Ankara allowing for the deportation from Greece back to Turkey of migrants who do not qualify for asylum.

In exchange, the EU has promised Turkey some €6bn over the next four years aimed at helping Turkey better conditions for the 2.7 million refugees it is hosting, as well as a conditional offer of visa-free travel for Turkish citizens.