European Union countries have begun the process of sending migrants who arrived in Europe via Greece over the last five months back to have their asylum applications assessed there.
EU rules oblige migrants to apply for asylum in the country they first enter. But the rules were suspended as hundreds of thousands of people, many Syrian refugees, entered Greece in 2015.
The European Commission says a number of EU countries have made requests to Greece to return migrants but that Athens must give assurances it has adequate reception facilities for them.
Commission spokeswoman Tove Ernst said Tuesday that the asylum rules were reintroduced in December but "it's not a full resumption, it's a gradual resumption."
Greece's asylum service says requests have been made to return more than 400 migrants.