Migrants enter a bus, which is supposed to leave to Austria and Germany, at the Keleti trainstation in Budapest, Hungary, September 4, 2015. [Photo/Agencies]

More than 140,000 migrants have been recorded entering Hungary so far this year through the EU's external border with Serbia, where Orban's government is building a 3.5-metre (11.5-foot) high wall. Countless others may have entered without registering.

Hungary says they have been spurred by Germany saying it would accept asylum requests from Syrian refugees regardless of where they enter the EU, contrary to EU rules.

On Friday, lawmakers adopted some of a raft of measures creating "transit zones" on the border, where asylum seekers would be held until their requests are processed and deported if denied.

The measures introduce jail terms for those who cross the border without permission or damage the fence, and may eventually provide for the use of the army.