ATHENS (Reuters) - Greece raged at neighbors and began bussing refugees and migrants back from its northern border on Tuesday, after new restrictions by countries on the main land route to Western Europe trapped hundreds behind a bottleneck at the frontier.

Athens filed a rare diplomatic protest with fellow EU member Austria for excluding Greek officials from a high-level meeting on measures aimed at curbing Europe’s biggest inward migration since World War Two.

More than a million migrants and refugees passed through Greece last year, and nearly 100,000 have already arrived this year. Nearly all reached Greece by sea and traveled onward by land over the Balkan peninsula to richer EU countries further north and west, above all Germany.

But several of the countries along that route have been taking new measures to close their frontiers, prompting those further down the chain to impose similar restrictions to prevent a bottleneck.

Greek police removed migrants from the Greek-Macedonian border on Tuesday after additional passage restrictions imposed by Macedonian authorities left hundreds of people, mainly Afghans, stuck at the border.

About 450 of them were loaded onto buses to be taken to reception centers in Athens, joining hundreds more fresh arrivals from outlying Greek islands who arrived on the Greek mainland on Tuesday morning.

As buses headed back south, hundreds more people were still traveling north toward the frontier, hoping for a chance to cross into Macedonia. Police occasionally supervised the privately-booked buses, which staggered their journeys to avoid congestion on the border.

At a petrol filling station at the community of Almyros, 270 kilometers north of Athens, up to 600 people, including Afghans, Syrians and Iraqis, waited for word on when their buses could continue the journey on to the Macedonian border.

“We were told Macedonia was closed,” said Fadi, a 40 year old Syrian who arrived in Greece through the island of Kos.

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He was on a bus which set off from Athens on Monday morning for a trip which normally lasts 7 hours. By Tuesday evening, he, his wife and three children had been on the road for 36 hours.

At the border with Macedonia on Monday, witnesses said Syrian refugees who did not have all travel documents, including passports, were turned back.

European countries are trying to slow the migration wave, which includes hundreds of thousands of refugees from Syria and other war zones, as well as large numbers of other migrants from north Africa, Central Asia and the Middle East.

Austria is due to host west Balkan states on Wednesday to discuss efforts to manage and curb the flow, but did not invite Greece. In unusually heated language that shows how the migration crisis has raised passions across Europe, Greek Foreign Minister Nikos Kotzias described the snub as a “unilateral and non-friendly act”.

“The exclusion of our country at this meeting is seen as a non-friendly act since it gives the impression that some, in our absence, are expediting decisions which directly concern us.”

Greece also accused its old foe Turkey of trying to “blow apart” an agreement that NATO would help patrol the porous sea border between Greece and Turkey to clamp down on human trafficking.

Turkey, which is hosting 2.5 million Syrians, the largest refugee population on earth, says it is trying to stop them from sailing for Greece but needs more aid.

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FINANCIAL CRISIS

Greece, still laboring under a financial crisis that has wrecked living standards at home, says it would not be able to cope with the influx on its own, if the onward passage of migrants through the Balkans is halted.

It says it cannot turn back thousands of people arriving on its shores daily in inflatable dinghies, citing international conventions.

Austria, the last country on the overland route to Germany, said last week it had imposed a daily limit of 3,200 migrants passing through, and 80 asylum claims.

Further down, Hungary has said it would shut three railway crossings with Croatia used by migrants, effective Feb. 22. Slovenia has erected a fence on its southern border with Croatia to ensure that migrants can enter only through official border crossings.

“The Balkan route was a humanitarian corridor. It could close after consultations and not by turning one country against the other,” Greek Migration Minister Yannis Mouzalas told Skai TV. “We are faced with an action that has elements of a coup.”

Vienna denied it had snubbed Athens by excluding it from Wednesday’s talks. The meeting of West Balkan nations was an established format which had first convened in Austria last year to discuss the issue of Islamist militants, a foreign ministry spokesman said.

The meeting includes interior and foreign ministers from Albania, Bosnia, Bulgaria, Kosovo, Croatia, Macedonia, Montenegro, Serbia and Slovenia.