1 million migrants arrived in Europe in 2015: UN

One million migrants and refugees arrived in Europe in 2015, according to the latest data from the United Nations (UN) and the International Organization for Migration (IOM).

In a joint statement on Tuesday, the UN and the IOM said that persecution, conflict and poverty had forced an "unprecedented" number of people to flee to Europe this year.

The vast majority of these people arrived by sea, with 972,500 having crossed the Mediterranean Sea as of December 21, according to UN figures. In addition, the IOM estimates that more than 34,000 people crossed from Turkey into Bulgaria and Greece by land in 2015.

Aris Messinis | AFP | Getty Images

Many thousands of these migrants are fleeing civil war in the Middle East or poverty in Africa. Most make the perilous journey across the Mediterranean Sea in order to reach southern European countries that are members of the European Union, such as Greece and Italy.

One-in-every-two of those crossing the Mediterranean this year – half a million people – were Syrians escaping the war in their country, according to the UN and the IOM. Of the rest, Afghans accounted for 20 percent and Iraqis for 7 percent.

The migrant crisis has been one of Europe's top concern this year, due to the dramatic rise in the numbers of people trying to reach its shores. Numbers crossing the Mediterranean increased steadily to a peak of more than 221,000 people in October from around 5,500 in January, according to the intergovernmental bodies.

More than 3,600 people died or went missing this year while crossing the Mediterranean Sea, the IOM and UN said.

The journey is highly dangerous and traumatic images of men, women and children who drowned have prompted emergency meetings of European leaders on how to deal with the crisis.

The issue has proved highly divisive, particularly in the wake of the Paris terrorist attacks and subsequent claims that jihadists had snuck into Europe in the guise of refugees.

In particular, the question of how to fairly distribute and rehouse possible refugees among the 28 nations within the European Union has proved divisive. Poorer Eastern European countries have rejected a quota system to receive people, saying it will only encourage more to come.

The IOM and the UN said that the number of people displaced by war and conflict this year was "the highest seen in Western and Central Europe since the 1990s, when several conflicts broke out in the former Yugoslavia."

The crisis has also highlighted painful truths about a rising tide of anti-immigration sentiment in Europe.

UN High Commissioner for Refugees António Guterres said in the joint statement on Tuesday that it was important to remember that migrants made a positive contribution to society.

"As anti-foreigner sentiments escalate in some quarters, it is important to recognize the positive contributions that refugees and migrants make to the societies in which they live and also honor core European values: Protecting lives, upholding human rights and promoting tolerance and diversity," he said.

- By CNBC's Holly Ellyatt, follow her on Twitter @HollyEllyatt. Follow CNBC International on Twitter and Facebook.