Orban has regularly crossed swords with the European Union over migrants, including by erecting fences on Hungary's border with Serbia.
"We have reinstated alien police detention in the cases of those whose application to enter Europe has not yet been legally judged," Orban told public radio in a regular interview.
"As long as there is a verdict outstanding (in their asylum applications) they cannot move freely in Hungary," said the 53-year-old known for his anti-immigration views. He gave no further details.
Under pressure from Brussels, the UN refugee agency and the European Court of Human Rights, Hungary in 2013 suspended the practice of detaining asylum applicants.
"But since then there have been terror acts in western Europe," Orban said Friday. "Any legal regulation that facilitates terror acts must be changed in the interests of our own self-defence."
He said he was aware that this "openly goes against the EU", putting his government in "open conflict" with the rest of the 28-nation bloc.
Orban has regularly crossed swords with the European Union over migrants, including by erecting fences on Hungary's border with Serbia and refusing to take part in a scheme to share refugees around the bloc.
Over the past two years many hundreds of thousands of migrants have sought asylum in Europe, many of them fleeing the civil war in Syria and other hotspots.
Orban says that allowing migrants in without proper checks poses a security threat, with some of the Islamist extremists responsible for attacks such as in Paris in November 2015 having posed as refugees.
The most recent attack was in Berlin on December 19 when a Tunisian, Anis Amri, drove a truck into a crowded Christmas market, killing 12 people. He was killed in a shootout with police in Italy four days later.
Amri arrived in Italy from Tunisia in 2011 and went to Germany in 2015. He was known to German counter-terrorism officials and was supposed to have been deported back to Tunisia.
Orban, a big admirer of US President-elect Donald Trump, also says that allowing in so many Muslims risks undermining Europe's democratic values and its Christian traditions.
Some of Orban's fiercest critics, not just over refugees but also in other areas, have been non-governmental organisations.
Earlier this week a senior member of his Fidesz party announced plans to tighten regulations on NGOs that receive foreign funding.
"We live in a world where attempts to influence are endemic in all countries," Orban said Friday.
"Hungarians have the right to know about actors in the public domain -- who gets what money from where, whether from abroad or from Hungary, and does the support come with expectations. We want transparency."