Geneva (AFP) - More than 700,000 refugees and migrants have reached Europe's Mediterranean shores so far this year, amid the continent's worst migration crisis since World War II, the UN refugee agency said Tuesday.

Some 562,355 people desperately fleeing war and misery reached Greece's shores, while around 140,000 arrived in Italy this year.

Taking into account arrivals in other European countries, the total number of people landing on the continent's shores was more than 705,200, the UN said.

Children made up 20 percent of the total arrivals.

A total of 3,210 have either died or gone missing as they made the journey plagued with danger.

More than half of this year's arrivals were from Syria, 18 percent from Afghanistan, and six percent from Iraq.

A total of 85 percent were from what the UN High Commissioner for Refugees (UNHCR) described as the world's 10 main refugee-producing countries.

As Europe struggles to deal with the crisis, the flow shows no sign of abating despite worsening weather conditions, according to the International Organization for Migration, which reported the arrival of 5,239 people in Greece on Saturday and 4,199 on Sunday.

"Because of the bad weather and rough seas, IOM staff report that tracking migrant boats at sea is becoming more difficult and more aerial surveillance is being implemented," the IOM said in a statement Tuesday.