Europe is "close to limits" on its ability to accept new waves of refugees, EU President Donald Tusk said Sunday, urging the broader international community to shoulder its share of the burden.

"The practical capability of Europe to host new waves of refugees, not to mention irregular economic migrants, is close to limits," he told a press conference on the sidelines of the G20 summit.

A steady stream of refugees has flowed into Europe over the last year, largely fleeing from the civil war in Syria.

The issue has become a political hot potato for leaders in the region as a series of Islamist terror attacks and rising anti-globalisation sentiment have combined to create an increasingly inhospitable environment for refugees from the brutal conflict.

The highly publicised drowning of a three-year-old Syrian boy last year temporarily softened hostility to migrants, after pictures of his corpse lying on a Greek beach rapidly became an emblematic image of the suffering involved in their journeys.

Germany threw open its borders and volunteers across Europe flocked to train stations and frontier crossings to welcome those fleeing war and poverty.

But a major backlash swiftly followed. The EU's outer borders have since come back down hard, the so-called Balkan migrant route has shut and anti-migrant sentiment has soared.

Tusk said there were 65 million displaced people around the world, and "the G20 community should scale up its share of responsibility".

"We have enough space for all parties to discuss these problems including China," he said, calling for financial assistance and development aid for migrants' countries of origin. "Only global efforts will be able to bear fruits."

Recent comments from leaders in Germany and Italy have signalled a hardening of attitudes about how to resolve the migrant crisis reshaping politics across Europe.

In March, the EU and Turkey signed a controversial deal aimed at stemming the flow of migrants to Europe.