Greece condemned the European Union on Monday for failing to fulfil its commitments to help ease pressure on Athens over migrants, a year after a burden-sharing agreement came into force.



"We are angry with Europe (because) it must finally meet its obligations," both in terms of transferring migrants and in terms of helping implement an EU-Turkey deal, migration minister Yannis Mouzalas told the Ert1 public TV channel.



He was commenting as a group of 111 Syrian refugees left Greece for Finland, under a program of redistributing migrants across the EU to share the burden of Europe's biggest migrant crisis since World War II.



"Today, a year after this program was launched," Athens' EU partners "have only taken charge of 5,000 refugees from Greece, while it promised to take in 33,000 of them" over the first year, and as many again between now and the end of 2017, he added.



Specifically he condemned the "sabotage" of the EU plan by the so-called Visegrad group of countries -- Hungary, Poland, the Czech Republic and Slovakia -- who are fiercely opposed to it, and against whom Athens is seeking EU sanctions.



The European Commission initially suggested that countries which fail to meet their obligations under the EU scheme could face financial penalties, but has not followed through on that warning.



Mouzalas blasted the lack of European support to implement the EU-Turkey deal, under which migrants who arrived in the Greek islands after March 20, including Syrian refugees, could be sent back to Turkey.



"The EU must support this agreement. It's not a question of showing solidarity with Greece. It's an obligation," he said.



Under the deal, the EU promised to provide experts to help Greece organise the return of migrants in line with asylum rules. But these reinforcements "are absent," he said.



Greek services are overwhelmed because most of the migrants have filed asylum requests in a bid to delay or block their return to Turkey, producing an "excessive concentration" in the Aegean islands, he said.



The presence of nearly 16,000 migrants there has prompted repeated spikes in tension, he said.



Athens wants to transfer some of these migrants to centres on the Greek mainland, but faces opposition from its EU partners who fear a mass resurgence of unregulated migrants heading north, he said.