A migrant smokes a cigarette as he waits among others to cross the Croatian border near the village of Berkasovo, Serbia October 19, 2015. Thousands of migrants clamoured to enter European Union member Croatia from Serbia on Monday after a night spent in the cold and mud of no-man's land, their passage west slowed by a Slovenian effort to impose limits on the flow to western Europe. (Photo by Marko Djurica/Reuters)

A Macedonian police officer hits a stranded migrant attempting to cross the Greek-Macedonian border, near Gevgelija, Macedonia December 2, 2015. Picture taken from the Greek side of the border. (Photo by Alexandros Avramidis/Reuters)

Migrants ride on top of a northern bound train toward the US-Mexico border in Juchitan, southern Mexico, Monday, April 29, 2013. Migrants crossing Mexico to get to the U.S. have increasingly become targets of criminal gangs who kidnap them to obtain ransom money. (Photo by Eduardo Verdugo/AP Photo)

Girls play in the makeshift refugee camp at the northern Greek border point of Idomeni, Greece, Thursday, March 17, 2016. Leaders of the EU's 28 divided nations reconvene in Brussels in hopes of ironing out disagreements on a proposed agreement with Turkey in the migrants crisis. (Photo by Vadim Ghirda/AP Photo)

Howard Jackson, a Liberian migrant, poses for a portrait in the Andalusian capital of Seville, southern Spain March 7, 2016. Jackson escaped civil war and spent three years crossing Africa before reaching Spain. Dressed up in one of his more than 200 costumes, from Peter Pan to Little Red Riding Hood, he is a well-known figure at an intersection entering the Spanish city of Seville where he has sold tissues to motorists for over a decade. Jackson is studying law and wants to become a judge. (Photo by Marcelo del Pozo/Reuters)

A migrant tries to restrain her tent from strong winds in a makeshift camp for refugees and migrants at the Greek-Macedonian border near the village of Idomeni, Greece, March 24, 2016. (Photo by Alexandros Avramidis/Reuters)

People stand by a damaged car at a train station at a makeshift camp for migrants and refugees at the Greek-Macedonian border near the village of Idomeni, Greece, May 10, 2016. (Photo by Marko Djurica/Reuters)

An officer of a Libyan anti-illegal immigrants unit conducts an early morning raid on migrants at hideout in Tripoli, Libya October 13, 2015. Libyan security forces charged with curbing illegal migration raided a hide-out for illegal migrants in Tripoli on Tuesday. (Photo by Hani Amara/Reuters)