(REUTERS)- It's from a scrubland around an old brick factory in northern Serbia that Syrian and Afghan migrants, escaping turmoil at home, hope to cross into nearby Hungary and into the European Union.

They wait in the shade for the cover of night, amid the litter of those who came before them.

Medical teams from Doctors Without Borders treat those worn out by the long journey. Ms Milena Radosavljevic from Medecins Sans Frontieres Doctor, said: "Most frequent are respiratory infections, stomach infections, problems with bones, fatigue from a long trip."

Migrants are entering Serbia as a transit point at a rate of more than 1,000 per day -- and that's just from its southern neighbor, Macedonia.

Across the Balkans, some 100,000 people are thought to have entered into Hungary illegally this year alone.

A migrant from Damascus in Syria, who declined to be named, said: "I will go to Hungary, after that to Austria, after that to Germany, because I want to go to university, maybe working. I just want a good life."

Their trek is about to get that much harder.

A month from now, Hungary will seal its border with Serbia with a barrier that is 175-kilometers long.

Hungary's right-leaning Prime Minister says Europe's migration policies are broken and that the influx of Muslim foreigners could distort Hungary's identity.

But Hungary is in the borderless Schengen zone and just too attractive to migrants, whom asylum workers say will simply bide their time. They say the barrier could create a migration 'bottleneck' in Serbia, right on Europe's fringes in a country ill equipped to cope.

Serbia's Minister for Social Policy Aleksandar Vulin said: "I am afraid we are going to face a humanitarian catastrophe when thousands of people who want to leave Serbia physically will not be able to."

Asylum experts also warn the barrier will push migrants into a 'grey zone' of illegality, where they can be preyed on by corrupted police and organised crime.

But for the migrants, these are all risks worth taking.