BERLIN (AFP) - The European Union's enlargement commissioner told the German Die Welt daily on Saturday that the next wave of migration to Europe could come from Syria's tiny neighbour, fragile Lebanon.

"Developments in Lebanon unsettle me. The situation there is... dramatic," Johannes Hahn told the conservative-leaning daily.

"The next wave of refugees might come from there," Hahn said.

More than four years into Syria's war, Lebanon has become home to more than 1.1 million Syrians living in grim conditions - making Lebanon's the highest refugee population per capita in the world.

"This country (Lebanon) has always been the most fragile of the region," Hahn said, noting his concern over its endemic "political instability".

"It also has a high unemployment rate and exorbitant public debt. It's a dangerous mix," he warned.

EU leaders have agreed to boost aid for Syria's neighbours, including one billion dollars through UN agencies, in a bid to mitigate the refugee influx into Europe.