IDOMENI, Greece -- Faced with yet another buildup of migrants caused by border restrictions in central Europe, police in Greece removed hundreds of Afghans from its border with Macedonia Tuesday after their route into Europe was blocked. Further north, police in the French port of Calais were preparing to evict people seeking to get to Britain from the shantytown known as the "jungle" that has developed into another flashpoint.

The seemingly arbitrary decision by some Balkan countries to close their borders to Afghans attempting to make their way across Europe to seek asylum has left thousands of people stranded in Greece, as more continue to arrive on Greek islands from the nearby Turkish shore.

Twenty-year-old Afghan Mirwais Amin said he was separated from relatives after being stopping from reaching the border and camping out at a nearby site.

"Macedonia isn't letting migrants through. I can't understand why," he said. "I can't get to the (border) camp, and members of my family are there. It's cold here and we have no food."

In Calais, authorities argue the sprawling "jungle" site presents sanitary risks and want to shut it down. Charity groups went to court to seek a last-minute delay of the evacuation. The court had been expected to rule Tuesday but announced that it would make no decision before Wednesday at the earliest.

Officials estimate 800 to 1,000 people currently live on the site, but humanitarian groups contend the figure is more than 3,000.

Regional administration head Fabienne Buccio said on Europe-1 radio Tuesday the expulsion order doesn't mean authorities will use force. Interior Minister Bernard Cazeneuve insisted the evacuation would be "progressive."

Maya Konforti of aid group L'Auberge des Migrants said volunteers would stand by the migrants if authorities try to force them out.

"We are going to be at their side, you know, no matter what. ... We are very suspicious but we are hopeful that they are going to be reasonable, because we are reasonable," she said.

The waves of refugees heading to Europe have increased in pace even compared with last year's massive influx, sorely testing European unity. Greece, with its extensive coastline and its islands' proximity to Turkey, is by far the favoured route.

The International Organization for Migration said Tuesday more than 102,500 people crossed into Greece between Jan. 1 and Monday, and about 7,500 into Italy. Such figures weren't reached last year until June. More than 1 million people crossed into Europe in 2015, more than 80 per cent of them reaching Greek islands from Turkey.

Despite initial welcoming overtures from some more prosperous European countries such as Germany, the sheer size of the flow has made nations balk at the prospect of having to integrate so many new arrivals.

Several countries have been distinctly hostile to the idea, and those along the Balkan route have successively closed their borders to certain nationalities. The latest are Afghans, who were not being allowed to cross Greece's border with Macedonia this week, leading to protests on the border and to the danger of thousands being stranded in the financially troubled country.

Greece on Tuesday slammed Austria for drastically restricting migrant crossings and for inviting officials from western Balkan countries to discuss the migration issue in Vienna but excluding Greece.

The foreign ministry described the meeting as a "unilateral move which is not at all friendly toward our country."

Austria's cap on the number of people it will admit each day prompted Macedonia last weekend to stop Afghan migrants from crossing, and to slow the rate at which asylum-seekers from Syria and Iraq were allowed across.

Faced with the buildup at the Greek-Macedonian border, police early Tuesday ordered mostly Afghan migrants onto Athens-bound buses. They were to be taken to an army-built camp near the capital that was set up last week, following European Union pressure on Athens to complete screening and temporary housing facilities.

The International Rescue Committee relief agency described Macedonia's decision as "yet another example of arbitrary, unilateral decisions by individual states threatening to cause serious humanitarian consequences for desperate refugees."

Bill Frelick, refugee program director at Human Rights Watch, accused EU countries of turning a blind eye to plight of Afghan asylum-seekers.

"Once again, Europe is resorting to closing its borders to asylum-seekers, instead of coming up with realistic policies to address the plight of those fleeing war and repression," he said.

Athens says it is shouldering a disproportionate burden in what is essentially a European refugee crisis, and has complained other EU countries have been painfully slow to fulfil pledges to accept asylum-seekers for relocation.

Seemingly frustrated by the slow pace of progress, Greece's Southern Aegean prefecture on Tuesday signed a bilateral agreement with Spain's regional authority of Valencia for the transfer of at least 1,000 refugees from Aegean islands to Valencia.

The agreement was signed on the tiny island of Leros, with the Southern Aegean regional authority saying the deal would be sent to the two countries' governments for ratification so it can be implemented.

Under the agreement, Valencia will arrange for a ship with a capacity of 1,000 people to sail from the Aegean islands to Spain, with the possibility of such a journey being repeated.

Becatoros reported from Athens. Derek Gatopoulos in Athens, Elaine Ganley in Paris, Sylejman Kllokoqi in Gevgelija, Macedonia and Dusan Stojanovic in Belgrade, Serbia, contributed