The row is the latest in a standoff between Brussels and Hungary — and several other East European states — over the migrations crisis. Hungary was quick to impose border controls as the migrant numbers crossing into Europe exploded in 2015, collapsing the Schengen "open borders" area.
It has also refused to take in migrants from other member states, according to a mandatory quota system demanded by the European Commission.
"Detaining asylum seekers simply because they are asylum seekers is a clear breach of EU and international law. It does not serve any purpose; on the contrary, it will lead to further trauma and despair," said Sophie in 't Veld, the Liberal and Democrats (ALDE) group vice-president.
"The Hungarian government has been fanning hostility to asylum seekers for years now, and again it seems to justify this measure by linking migration with terrorism. That is unacceptable."
"We urge the European Commission to act swiftly and with determination. The Commission has been ignoring reports pointing out human rights violations. It has also turned a blind eye to breaches of EU and international law in Hungary. The Commission has the obligation to act," she said.
Quota Rowroadmap for migrants, allowing for the relocation of 160,000 migrants who had turned up in various countries — notably Greece, Italy and Hungary — amid the chaos of mass movement and inadequate border controls. These migrants would be "processed" and then redistributed around EU member states according to an "emergency" plan mandatory quota system.
The plan was supposed to have relocated the migrants within two years — by September 2017 — but only 13,956 have, so far, been relocated out of Greece and Italy, according to the latest figures (March 3). Many member states are opposed to the mandatory quota system, with Austria, Hungary and Poland refusing to take any.