The two countries said the measures were necessary to protect their farming sectors from cheap imports.

The ban applies to grains, dairy products, sugar, fruit, vegetables and meats and will be in force until the end of June.

The Commission said it was not up to individual member states to make trade policy.

While the Commission has said that unilateral moves will not be tolerated, it has not yet specified what measures it would take against Poland and Hungary.

"In such challenging times, it is crucial to coordinate and align all decisions within the EU," its spokesperson said in a statement.

Most Ukrainian grain is exported via the Black Sea, but Russia's invasion last year disrupted export routes and resulted in large quantities of the grain ending up in central Europe.

A deal with Russia, brokered by the UN and Turkey, allows Ukraine to continue exporting by sea - but Ukraine accuses Russia of slowing the process with over-zealous inspections.

Poland and Hungary announced the move on Saturday. The decision came after complaints from local farmers who said they were being undercut by cheaper Ukrainian grain flooding their markets.

On Sunday, Polish Economic Development and Technology Minister Waldemar Buda clarified that the ban applied to goods in transit as well as those staying in Poland.

He called for talks with Ukraine to set up a scheme to ensure exports pass through Poland and do not end up on the local market.

Ukraine says the move contradicts bilateral trade agreements.

A statement by Ukraine's Agriculture Ministry said it had "always been sympathetic to the situation in the Polish agricultural sector and responded promptly to various challenges".

"At present, unilateral drastic actions will not accelerate the positive resolution of the situation," it added.

Ministers from Poland and Ukraine are due to meet to discuss the issue in Poland on Monday.