A fence on the Serbian border to stem the flow of migrants and refugees will be built within a few months, beginning with the areas most used by human smugglers, Hungary's foreign minister said Thursday.

Peter Szijjarto said that the 4-meter (13-foot) high fence would "defend Hungary and the European Union from the startling scale of illegal immigration pressure." Szijjarto said that police had detained more than 68,000 people who according to the government entered Hungary illegally this year, nearly all arriving from Serbia.

"The work will start at eight to 10 locations at the same time ...  in the areas most exposed to the immigration pressure," Szijjarto said on state television. "This means the areas most used by human traffickers."

Meanwhile, the U.N. refugee agency urged Hungary to refrain from implementing a plan which could make its asylum system more restrictive for refugees, saying the "proposals would have devastating implications" for them.

Hungarian lawmakers are expected to soon debate draft legislation from the Interior Ministry which, among other measures, would allow authorities to detain asylum seekers for prolonged periods and restrict the right of those making repeated asylum claim to remain in Hungary while their cases are decided.

"We fear that the new amendments will make it impossible for people fleeing war and persecution to seek safety in this country," Montserrat Feixas Vihe, the UNHCR's regional representative for Central Europe, said in a statement. "We understand Hungary's national security concerns, but this should not victimize the victims."