Mass cross-border migration is an "unavoidable reality" and it is "impossible to stop" the flow of refugees in need of sanctuary, the United Nations’ top official in charge of migration said during a visit to Bangladesh.

Mass cross-border migration is an "unavoidable reality" and it is "impossible to stop" the flow of refugees in need of sanctuary, the United Nations' top official in charge of migration said during a visit to Bangladesh.

In an interview with AFP in Dhaka, Peter Sutherland, the UN's special representative for migration, said the world needed to accept millions of people fleeing conflicts in Syria and elsewhere and find ways to live together.

Sutherland is visiting Bangladesh for the Global Forum on Migration and Development in Dhaka where he said he would discuss the plight of Rohingya refugees in Bangladesh.

The refugees, fleeing ongoing persecution in Myanmar have been living in Bangladeshi camps or jungle hideouts, some for generations, often without access to basic food or shelter.

The forum in Dhaka takes place as Europe is facing its biggest migration crisis since World War II, with more than a million asylum seekers arriving in Germany alone in 2015 -- triggering a fierce backlash.

"We must find ways to be living together. Today (migration) is an unavoidable reality, we are living in the era of globalization," Sutherland said in the Bangladeshi capital late on Thursday.

"It is impossible to stop. Those who believe in some way that we can erect fences and stop migration are living in Cloud Cuckoo Land," he said.

Turkey is currently hosting 2.2 million Syrian refugees, while between 2,000 and 3,000 people arrive daily in the main European landing point of Greece, although many die making the journey.

Sutherland criticized world leaders who stoke xenophobia for political gain and link refugees with a heightened terror threat.

"They represent the world of yesterday, a world of conflict and not a world of consensus. They represent a world which creates division rather than harmony," he said.

"Humanity demands responsibility and care for those who need sanctuary."  

The European Union's passport-free Schengen area has come under huge strain from the migrant influx, with wealthier countries including Denmark and Sweden introducing border controls to deal with the flow of people.