The United Nations Refugee Agency said in a report released Wednesday that “Europe is living through a maritime refugee crisis of historic proportions.”

The number of people, the agency reported, attempting to cross the Mediterranean Sea to Europe swelled 83-percent to over 135,000 in the first half of 2015, compared with the same time last year.

The organization expects the situation to worsen as favorable summer weather allows people smugglers to dispatch more immigrants, often in unseaworthy boats.

Illegal immigration is a major concern for the European Union, where member states are debating how best to tackle human trafficking and how to share the burden of assisting new arrivals.

Growing numbers of immigrants are reaching the shores of Italy and Greece, before moving on to other northern European countries in a bid to find employment, sparking objections and growing anti-foreigner sentiment in many EU countries.

The UN's report hailed Brussels' decision to resettle 40,000 Syrian and Eritrean asylum seekers who have already arrived in Europe, but called for greater cohesion between states to assist both immigrants and the countries carrying the heaviest load.

Agency head Antonio Guterres stressed that many of the people arriving by boat in Europe were not economic migrants.

"Most of the people arriving by sea in Europe are refugees, seeking protection from war and persecution," he said in a statement.

The refugee agency reported that a third of those who arrived by sea in Italy or Greece in the first half of this year came from war-ravaged Syria, while people fleeing violence in Afghanistan and Eritrea's repressive regimes made up 12-percent of new arrivals.

Other main countries of origin include war-torn Somalia, Nigeria, Iraq and Sudan, the report said.

DW