A single, narrow border crossing between Serbia and Croatia was opened overnight for passenger traffic, but cargo trucks remained blocked in a deepening dispute between the ex-Yugoslav republics over the flow of migrants across their joint frontier. Serbia has set a midnight deadline for Croatia to lift a blockade on cargo traffic from Serbia, imposed in retaliation for Serbia directing the flow of migrants across the Croatian border. Croatia had already closed seven of eight border crossings to traffic, and late on Tuesday the eighth was closed by protesting truck drivers. More than 30,000 migrants, many of them Syrian refugees, have entered European Union member Croatia from Serbia since Tuesday last week, when Hungary barred their entry to the EU by sealing its southern border with Serbia with a metal fence. They are being bussed by Serbia direct to the Croatian border, having entered Serbia from Macedonia, and trekking through fields beyond the official border crossings. Croatia says it cannot cope with the numbers, saying Serbia should send them to Hungary and Romania too. Sleeping in Cemetery Both Serbia and Croatia were part of socialist Yugoslavia but Croatia broke away in 1991 and fought a war against Belgrade-backed Serb rebels until 1995. Croatia joined the EU in 2013, and Serbia wants to follow suit. With a queue of trucks on the Belgrade-Zagreb highway 12 km (7 miles) long, Serbia gave Croatia until the end of Wednesday to lift the cargo blockade or face political, legal and economic retaliation. “Serbia must reply to the destruction of its economic integrity and national policy,” Serbian Prime Minister Aleksandar Vucic said on Tuesday. Croatia on Tuesday eased the blockade to allow through only trucks carrying perishable goods. In protest, frustrated drivers parked several trucks in no-man’s land across the main Bajakovo-Batrovci crossing, halting all road traffic. “We had to do it,” said a driver from the Serbian town of Novi Pazar who gave his name as Emin. “We’ve been here for almost three days and no one even come to ask us whether we’re hungry or thirsty or to bring us anything.” Croatian authorities later opened the nearby Tovarnik-Sid crossing to passenger traffic, but not trucks. Croatia is sending migrants north across its own border with Hungary – which in turn sends them to Austria – but is struggling to keep pace with the influx. A camp opened in Opatovac in eastern Croatia is fast reaching capacity, while thousands are stuck in no-man’s land between Sid and Tovarnik, some sleeping in a cemetery.