The European Union is proposing increased humanitarian aid for Greece, where more than 20,000 refugees and migrants are stuck after borders were tightened along the Balkans preventing them from trekking north to wealthier parts of Europe.

The European Commission, the EU executive, said on Tuesday it will put forward a plan on Wednesday to offer emergency financial assistance for humanitarian crises inside the 28-nation bloc, comparable with operations it has launched elsewhere in the world.

The Commission's spokesman, Margaritis Schinas, told a regular news briefing in Brussels that the plan was necessary "to prevent humanitarian suffering as a result of an unprecedented number of people arriving in the EU".

Schinas said the Commission was very concerned with the outbreak of violence at the Greek-Macedonian border. He was speaking as the bloc is gearing up to a summit on Monday with Turkey, the main departure site for the vast majority of people heading to Europe.

More than a million refugees and migrants arrived in Europe last year -- mostly via Turkey to Greece -- and another 130,000 have reached the continent so far in 2016.

Overwhelmed, Greece and other countries along the main migration route have tended to wave the people through and the influx has brought Europe's Schengen zone of free travel to the verge of collapse.

European Commission President Jean-Claude Juncker talked to Greek Prime Minister Alexis Tsipras on Monday and European Council President Donald Tusk will visit Austria, Slovenia, Croatia, Macedonia, Greece and Turkey this week.

Brussels and Berlin, which are battling to make a joint European plan to alleviate the migration crisis work, are banking on Turkey to sharply reduce the number of people embarking for Europe, many of whom have fled the war in Syria.

But a growing number of EU states are resorting to unilaterally tightening their own borders, seeking to control the flow of people and prevent a spike in the arrivals many expect later in March as the weather improves.

Austria, the last stop for refugees and migrants heading to their top destination Germany, infuriated Athens, Berlin and Brussels last month by announcing daily caps on the number of people it processes.

Chancellor Werner Faymann defended the step, saying Austria cannot become a waiting room for Germany.

Tusk, in Vienna on the first leg of his pre-summit tour along the Balkans migration route, said after talks with Faymann: "We must face together the consequences of our decisions. The country that we must support in particular is Greece."