LUXEMBOURG - The European Union stepped up pressure Wednesday on rebellious eastern states to take in their fair share of refugees under mandatory quotas adopted at the height of the migrant crisis.

Hungary and Slovakia looked set to see their appeal against the plan rejected after the advisor to the EU’s top court said the quotas were a fair way of easing the pressure on Greece and Italy.

The European Commission meanwhile took its landmark legal action against Poland, Hungary and the Czech Republic to the next level over their refusal to take in any asylum-seekers under the system.

Judges also upheld the bloc’s rules saying that asylum claims must be dealt with by the country where refugees first land. They said Croatia must accept migrants deported back from Austria and Slovenia.

A wave of people fleeing the war in Syria and conflict and poverty in other Middle Eastern and African countries in 2015 triggered Europe’s biggest migration crisis since World War II.