German police lead arriving migrants across a field to a transport facility, in October last year | Johannes Simon/Getty images Germany suspends migrant returns to Hungary Hungary’s been criticized for detaining migrants in camps on its border with Serbia.

Germany has stopped sending migrants back to Hungary until it can be sure that those transferred "will be dealt with according to European procedures," a spokesperson for the German interior ministry said Tuesday, according to BFMTV.

"Without such assurance," the spokesperson said, "there would no referrals until further notice."

Hungary, which recently began to detain migrants in camps on its border with Serbia, was widely criticized by human rights groups which believe the measures violate international and EU law.

Filippo Grandi, the United Nations' refugee agency's chief, on Monday called for a suspension of all transfers of asylum seekers "until the Hungarian authorities bring their practices and policies in line with European and international law."

According to BFMTV, Germany returned 294 asylum seekers to Hungary in 2016.