Four Balkan countries have begun turning back migrants who do not come from Syria, Iraq or Afghanistan.
The move left thousands of people stranded on borders.
Greek police said the border area of Idomeni has been essentially shut down since about 8 a.m. after about 300 people were denied access. Another 2,500 people are waiting at a camp nearby that offers temporary shelter for those heading through the Balkans to nothern Europe.
On Serbia’s border with Croatia about 400 people were denied passage to north Europe. They were stopped by Croatian police when they tried to cross the border through fields.
Slovenia has also said it plans to deport economic migrants, but Croatia refused to take the first group of 162 back, underlining the urgent need for a coordinated plan to transport migrants back to Turkey.
The Balkan states have been embroiled in conflicts and stranded migrants trapped within nation states could reignite tensions.
In addition, Greece could soon find hundreds of thousands, if not millions of migrants, stranded in its borders unless Greek Prime Minister Alexis Tsipras reinstates former border control measures.