Hungary is exacerbating the problem of people-smuggling with its plan to build a barrier to restrict the flow of migrants and refugees into the country, the International Organisation for Migration said on Friday. Hungary, which is part of Europe’s passport-free Schengen travel zone, is building a 3.5-metre high fence along its 175-km (110-mile) border with Serbia, taking a hard line on what right-wing Prime Minister Viktor Orban says is a threat to European security, prosperity and identity. The IOM says 1,500-2,000 are taking the route through Greece, Macedonia and Serbia to Hungary every day and that there is "a real possibility" the flow could rise to 3,000 daily.