BELFAST, Northern Ireland — More than 16 years after the Good Friday peace deal brought real hope that Protestants and Roman Catholics could live together in relative harmony, Northern Ireland is being racked by another wave of violence.

But this time it is not driven by the sectarian divide, but by animosity toward a fast-growing population of immigrants — adding one more challenge as Europe struggles to cope with the combination of intense economic strain and rapid demographic change.

“This is a society that always prides itself on being very friendly, but it is becoming less and less welcoming, particularly to certain types of people,” said Jayne Olorunda, 36, whose father was Nigerian, and though she grew up in Northern Ireland said her color has always marked her as an outsider.

The expanding problem appears to be partly racial and partly directed at immigrants of all backgrounds at a time when open borders in the European Union have led more legal migrants to Britain and Ireland in search of work. At the same time, war and economic deprivation have driven waves of legal and illegal migrants toward Europe from Asia, the Middle East and Africa. The more recent immigrants from Eastern Europe and parts of Africa tell stories similar to those of people from China, India and Pakistan who have lived here for decades.