Hungary's army has begun exercises to prepare for a possible future role in guarding the southern border to try to stem the influx of migrants.
Budapest plans to send soldiers to help police at the border where thousands of migrants arrive from Serbia every day.
A new razor-wire barrier is already being built along the frontier. MPs are expected to vote on stricter border controls later this month.
The plans for militarisation have been criticised by human rights groups.
Meanwhile the authorities in Hungary have been told to expect 40,000 more migrants by next week.
The BBC's Bethany Bell at the Austria-Hungary border reports that hundreds more people have arrived there and that 3,500 had crossed into Austria overnight.
Many migrants are fleeing conflicts in countries like Syria and Libya and are trying to travel through Hungary to Germany, Austria and Sweden - wealthier EU nations with more liberal asylum laws.
In other developments:
• Another group of 2,500 migrants boarded a ferry hired by the Greek government early on Thursday morning to transport them from the island of Lesbos to the mainland
• Denmark earlier suspended all rail links with Germany and temporarily closed a motorway after police stopped hundreds of migrants trying to reach Sweden at the border. Trains are to resume after some migrants agreed to register in Denmark and others were driven away in cars
• The Irish government has announced it will take in 4,000 refugees - the figure includes 1,120 people Ireland has already agreed to receive
• The European Commission earlier proposed that 120,000 additional asylum seekers should be shared out between 28 members of the EU.
Source : BBC