Migrants trudge through Balkans in 'dramatic' challenge to Europe

Police let migrants pass the border line from Greece to Macedonia, near Gevgelija August 24, 2015. REUTERS/Ognen Teofilovski

MIRATOVAC, Serbia (Reuters) - Long lines of migrants, many of them refugees from Syria, snaked through southern Serbia by foot on Monday before jumping on trains and buses north to Hungary and the last leg of an increasingly desperate journey to western Europe.

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 overwhelmed islands to the mainland.