Germany's Interior Minister Thomas de Maizière said on Friday that the EU-Turkey migrant deal is working, while he expressed concern about the numbers coming from Italy and Libya.
Migrants should no longer be able to get to Germany and Europe via the Balkan route, de Maiziere said.
"It's clear that the Balkan route is a thing of the past and no longer will or should be a place again from where people will be waved through to Germany and Austria and to the centre of Europe," he said at a news conference in Potsdam.
"Now the issue is alternative routes - on the Balkan route and also we are of course concerned that we'll get rising refugee numbers again as they come via Libya and Italy," he added.
The latest figures from Turkey's Coast Guard show that the EU-Turkey deal is working, with the number of migrants intercepted at sea only 1,536 in April, a substantial decline compared to the more than 8,100 people intercepted in March.