Migrants from Syria rest at a park in Belgrade, Serbia, Wednesday, Aug. 26, 2015 (AP)

Hungarian police speak to a group of migrants on the border line at the railway tracks leading from Serbia into Hungary, near Horgos, Serbia, Friday, Aug. 28, 2015 (AP)

A migrant passes by the Hungarian police on the other side of the border fence near Horgos, Serbia, Friday, Aug. 28, 2015 (AP)

A migrant family sleeps in a park near the main bus and train station in Belgrade, Serbia, August 26, 2015 (Reuters)

A migrant from Syria gets a haircut at a park in Belgrade, Serbia, Friday, Aug. 28, 2015 (AP)

Hungarian policemen arrest a Syrian migrant family after they entered Hungary at the border with Serbia, near Roszke, August 28, 2015( Reuters)

Hungarian border police officers guard the border fence along Hungary's border with Serbia, near Horgos, Serbia, Friday, Aug. 28, 2015 (AP)

Migrants from Syria sleep at a park in Belgrade, Serbia, Thursday, Aug. 27, 2015 (AP)

A migrant from Syria washes his face at a park in Belgrade, Serbia, Wednesday, Aug. 26, 2015.(AP)

Syrian refugees cross into Hungary underneath the border fence on the Hungarian - Serbian border near Roszke, Hungary on Aug. 26, 2015 (AP)

A migrant woman holding her child's hand waits in front of Hungarian policeman on the border line at the railway tracks leading from Serbia into Hungary, near Horgos, Serbia, Friday, Aug. 28, 2015.(AP)

Hungarian police stand on the border line at the railway tracks leading from Serbia into Hungary, near Horgos, Serbia, Friday, Aug. 28, 2015 (AP)

Migrants from Syria warm themselves by a fire at a park in Belgrade, Serbia, Thursday, Aug. 27, 2015 (AP)

A migrant family sleeps in a park near the main bus and train station in Belgrade, Serbia, August 26, 2015 (Reuters)

In this Monday, Aug. 17, 2015 photo, Syrian girl Rahaf Kaddour, 5, who was burnt in an explosion that hit her home, poses for a picture at MSF Hospital for Specialized Reconstructive Surgery in Amman, Jordan. In Syria alone, more than 1 million have been wounded in the war since 2011(AP)

A migrant takes a selfie by the border fence along Hungary's border with Serbia, near Horgos, Serbia, Friday, Aug. 28, 2015 (AP)

A migrant from Syria carries his child in his arms at a bus station in Belgrade, Serbia, Friday, Aug. 28, 2015 (AP)

A migrant from Syria sleeps at a park in Belgrade, Serbia, Wednesday, Aug. 26, 2015(AP)