Hungary announced on Monday that it was ready to enforce a controversial law to detain asylum-seekers in camps on its southern border with Serbia.
The law, approved by Hungary's parliament on March 7, has drawn criticism from human rights groups and the UN.
It calls for a systematic detention of all asylum-seekers in camps composed of converted shipping containers.
Starting Tuesday, asylum-seekers entering the country as well those currently there will be held in camps while their applications are processed.
"The police, the defence forces and the Immigration and Asylum Office have made the necessary preparations for the implementation of the required measure," said a statement by the interior ministry.
EU member Hungary previously systematically detained all asylum applicants but suspended the practise in 2013 under pressure from Brussels, the UN refugee agency and the European Court of Human Rights.
According to the government, 324 shipping container homes have been installed at two separate locations called "transit zones", built into a fence that Hungary erected along the 175-kilometre (110-mile) long border in 2015.
A second "smart fence", complete with night cameras, heat and movement sensors, and multilingual megaphones warning against crossing the barrier is also under construction, with completion scheduled for May.
The UN High Commissioner for Refugees has said that systematic detention will "have a terrible physical and psychological impact on women, children and men who have already greatly suffered."