Thousands of migrants, many of them refugees from Syria, are walking into southern Serbia, on the latest leg of an increasingly desperate journey to western Europe. State authorities and aid agencies scrambled to help the tired masses surging through the western Balkans. Their numbers have swelled since Greece began ferrying migrants from overwhelmed islands to the mainland.

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Syrian refugees walk along a road towards the town of Presevo in southern SerbiaMarko Djurica/Reuters
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Syrian refugees rest in a shady spot in the town of Presevo, SerbiaMarko Djurica/Reuters
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Migrants and refugees wait to be registered in a camp in the southern Serbian town of PresevoArmend Nimani/AFP
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Migrants and refugees in the southern Serbian town of Presevo board a bus heading to BelgradeArmend Nimani/AFP

Red Cross official Ahmet Halimi said 8,000 migrants had registered in the southern Serbian town of Presevo over the past 24 hours. In the past two weeks, over 23,000 have entered Serbia, taking the total so far this year to 90,000.

Many had spent three desperate days on Greece's northern border after Macedonia halted their passage saying it could take no more. But crowds braved batons and stun grenades to storm through police lines. Helpless to stem the tide, Macedonia rushed trains and buses to the border to carry them north, where they crossed into Serbia on foot.

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Migrants and refugees hold their passports as they are held at the Greek-Macedonian borderOgnen Teofilovski/Reuters
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A little girl cries as she waits with her family to be allowed entry to MacedoniaOgnen Teofilovski/Reuters
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A Macedonian police officer raises his baton in an attempt to stop refugees and migrants from entering the countryAlexandros Avramidis/Reuters
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Migrants try to avoid tear gas deployed by Macedonian policeAlexandros Avramidis/Reuters
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Macedonian police officers try to control refugees and migrants as they cross the border between Greece and MacedoniaRobert Atanasovski/AFP
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A woman carries her child as the rain falls near the border crossing between Greece and MacedoniaAlexandros Avramidis/Reuters
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A woman and child wait to cross into Macedonia from GreeceRobert Atanasovski/AFP
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Men sleep as they wait for a train to Serbia in the town of Gevgelija, on the Macedonian-Greek borderRobert Atanasovski/AFP
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Migrants and refugees arrive at a railway station in Gevgelija, MacedoniaRobert Atanasovski/AFP
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Migrants and refugees wait for their transit documents at a newly built registration centre near Gevgelija, MacedoniaOgnen Teofilovski/Reuters
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Migrants gathered on a platform at the train station in Gevgelija wait for police officers to give them permission to board a train to SerbiaRobert Atanasovski/AFP
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Police officers allow a group of migrants and refugees to board a train in GevgelijaRobert Atanasovski/AFP
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Migrants board a train for Serbia from Gevgelija, on the Macedonian-Greek borderRobert Atanasovski/AFP
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A migrant tries to get onto a train heading to Serbia from the station in Gevgelija, on the Macedonian-Greek borderDimitar Dilkoff/AFP
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Migrants and refugees wait to board a train to Serbia in the new reception centre near the town of GevgelijaRobert Atanasovski/AFP

Their first stop in Serbia was a reception centre in Presevo, where many received medical aid, food and papers legalising their transit through the country.

Not since the wars of Yugoslavia's collapse has the western Balkans seen such large movements of people. In the early 1990s many Bosnians, Croats, Albanians and Serbs displaced by fighting fled for wealthy countries such as Germany, Austria and Sweden – the very countries that the current wave of migrants favour. Germany says it expects a record 750,000 asylum-seekers to arrive this year.

The refugees' plight threatens to get worse as Hungary, part of Europe's borderless Schengen zone, races to complete a fence along its 175-km border with Serbia, threatening to create a dangerous bottleneck. Every day, around 1,500 refugees stream through the woods from Serbia into Hungary. While the country is a transit route rather than a destination for most, the growing influx is polarising Hungarians and fuelling racism.