Imagine the entire population of Britain uprooted: The U.N. refugee agency says just over that number -- 65 million people -- were displaced worldwide by the end of last year, easily setting a new postwar record, as it warned that European and other rich nations can expect the tide to continue if root causes aren't addressed.

In a year when more than a million people arrived on European shores, UNHCR said continued conflicts and persecution in places like Syria and Afghanistan fueled a nearly 10-percent increase in the total number of refugees and internally displaced people in 2015.

"I hope that the message carried by those forcibly displaced reaches the leaderships: We need action, political action, to stop conflicts," said Filippo Grandi, the U.N. High Commissioner for Refugees. "The message that they have carried is: `If you don't solve problems, problems will come to you."'

The figures are contained in the Geneva-based agency's latest Global Trends Report issued Monday, timed for World Refugee Day. They show that for the first time since World War II, the 60 million mark was crossed, even topping the equivalent of the total U.K. population of about 64.6 million.

"If these 65.3 million persons were a nation, they would make up the 21st largest in the world," the report said.

With stark detail, UNHCR said that on average, 24 people had been displaced every minute of every day last year -- or 34,000 people a day -- up from 6 every minute in 2005. Global displacement has roughly doubled since 1997, and risen by 50 percent since 2011 alone -- when the Syria war began.

About 11.5 million people from Syria had fled their homes: 6.6 million within the war-ravaged country and 4.9 million abroad. More than half of all refugees came from three countries: Syria, Afghanistan and Somalia, and more than half of all displaced people were children, UNCHR said.

Turkey was the top host country for the second year running, taking in 2.5 million people -- nearly all from neighboring Syria. Afghan neighbor Pakistan had 1.6 million, while Lebanon, next to Syria, hosted 1.1 million. UNHCR said the total figures of forcibly displaced people amounted to about one in every 113 people on the planet.

Grandi said policymakers and advocacy groups admittedly face daunting challenges in helping the largest subset of displaced people: Some 40.8 million internally displaced in countries in conflict. Another 21.3 million were refugees and some 3.2 million more were seeking asylum.

More than a million people fled to Europe last year, causing a political crisis in the EU -- with Greece and Italy facing the initial brunt, Germany welcoming in hundreds of thousands, and some eastern European countries erecting strict barriers to block the flow.

Concerns about immigration have affected the debate in Britain about whether to remain in the European bloc ahead of Thursday's Brexit referendum.

So far this year, the flow of refugees into Europe has eased through the Turkey-to-Greece route that was the dominant thoroughfare last year. A recent EU-Turkey deal allows Greece to return Syrian asylum-seekers to Turkey without evaluation of their protection claims on the basis it is a "safe third country."

Human Rights Watch on Monday urged the EU to evaluate Syrian refugees' protection claims on the merits.

Grandi called on countries to work to fight the xenophobia that has accompanied the rise in refugee populations, and decried both physical barriers -- like fences erected by some European countries -- as well as legislative ones that limit access to richer, more peaceful EU states.

Such European policies were "spreading a negative example around the world," he said.

"There is no plan B for Europe in the long run," Grandi said. "Europe will continue to receive people seeking asylum. Their numbers may vary ... but it is inevitable."