Migrants from Syria walk in Macedonia near the Greek border June 17, 2015. Hungary announced plans to build a four-metre-high fence along its border with Serbia to stem the flow of illegal migrants. REUTERS/Ognen Teofilovski

An Afghan woman carries her child while walking along a road after crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 18, 2015. Hungary says almost 60,000 migrants have entered the country illegally so far this year.

Migrants from Syria ride their bicycles on the motorway Alexander of Macedonia in central Macedonia June 18, 2015. Forbidden from using public transport in Macedonia, thousands of migrants, most of them Syrians, are taking to two wheels to cross this landlocked republic en route to Serbia, then Hungary and Europe s borderless Schengen zone. REUTERS/Ognen �Teofilovski

A migrant from the Democratic Republic of Congo rests in Macedonia near the Greek border June 17, 2015. REUTERS/Ognen Teofilovski

An Afghan girl stands on a road after crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 18, 2015. REUTERS/Bernadett Szabo

Iraqis wait as they are detained by Hungarian police after crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 18, 2015. REUTERS/Bernadett Szabo

Iraqis wait as they are detained by Hungarian police after they crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 18, 2015. REUTERS/Bernadett Szabo

A migrant from Syria carries his bicycle on railway near the Greek border in Macedonia June 17, 2015. REUTERS/Ognen Teofilovski

Afghans walk along a road after crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 18, 2015. REUTERS/Bernadett Szabo

A migrant from the Democratic Republic of Congo rests in Macedonia near the Greek border June 17, 2015. REUTERS/Ognen Teofilovski

Immigrants from Syria stand near their bicycles as they hide from the rain under a bridge near the Greek border with Macedonia, June 17, 2015. REUTERS/Ognen Teofilovski

A migrant walks in Macedonia near the Greek border June 17, 2015. REUTERS/Ognen Teofilovski

Migrants from Syria ride their bicycles near the Greek border in Macedonia June 17, 2015. REUTERS/Ognen Teofilovski

Afghans wait as they are detained by Hungarian police after crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 18, 2015. REUTERS/Bernadett Szabo

Migrants from Syria walk in Macedonia near the Greek border June 17, 2015. REUTERS/Ognen

Migrants from Syria ride their bicycles near the Greek border in Macedonia June 17, 2015. REUTERS/Ognen Teofilovski

Migrants from the Democratic Republic of Congo rest in Macedonia near the Greek border June 17, 2015. REUTERS/Ognen Teofilovski

Migrants from Syria ride their bicycles near the Greek border in Macedonia June 17, 2015. REUTERS/Ognen Teofilovski

A group of Afghans walk along a road after crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 18, 2015. REUTERS/Bernadett Szabo

Migrants from Syria ride their bicycles near the Greek border in Macedonia June 17, 2015. REUTERS/Ognen Teofilovski

A migrant from Syria carries his child at Demirkapija train station in Macedonia June 17, 2015. REUTERS/Ognen Teofilovski