The UN refugee agency is warning of a `"build-up'' of migrants in Serbia as its neighbours tighten their borders.
Adrian Edwards of UNHCR said the crisis “is growing and being pushed from one country to another” as about 4,000 migrants pour into Greece each day and head north.
He says stricter border controls by Hungary and Croatia threaten a bottleneck in Serbia, “which is not a country with a robust asylum system”.
Mr Edwards said: “You aren’t going to solve these problems by closing borders.”
UNHCR says more than 442,440 people have crossed the Mediterranean this year, and 2,921 have died trying.