The U.N. refugee agency says changes to Hungary's asylum system being rushed through parliament and the government's plan to build a fence on the border with Serbia could have "fatal consequences" for refugees fleeing war.

Montserrat Feixas Vihe, the UNHCR regional representative in Central Europe, says in an open letter to Hungarian lawmakers published Friday that while every country has the right to defend its borders and protect its citizens, the planned amendments "would make it impossible for people fleeing persecution to access international protection in Hungary."

Over the past year, some 100,000 migrants and refugees have reached Hungary.

Parliament voted Friday to fast-track amendments proposed by the Interior Ministry which, for example, would allow authorities to detain asylum seekers for prolonged periods.