Migrants standing at the Greek side of the border wait to cross into Macedonia, near Gevgelija August 24, 2015. State authorities and aid agencies threw up tents and scrambled to supply food and water to thousands surging through the western Balkans, their numbers swelling since Greece began ferrying migrants from its overwhelmed islands to the mainland. The United Nations refugee agency, UNHCR, said more than 7,000 had reached Serbia from Macedonia between Saturday and Sunday, many of them having spent three desperate days on Greece's northern border after Macedonia halted their passage saying it could take no more. REUTERS/Ognen Teofilovski - RTX1PFAC