Why are migrants storming the Greece-Macedonia border?

Migrants hoping to travel through Greece into Europe have been stalled for days at its northern border, as many neighboring nations have tightened their borders.

Iraqi and Syrian refugees, stuck for days at Greece’s border with Macedonia, tore down a metal gate at a boundary fence on Monday in a frustrated attempt to break through, but were met by police who repelled the crowd.

More than 22,000 migrants were trapped in Greece Monday, according to Reuters, with many forced to sleep in places like the Olympic venues from the 2004 Athens Games or makeshift refugee camps with few resources.

The thousands continuing to pour in from North Africa and areas of conflict in the Middle East have made Greece a flash point for migration through Europe, as it is one of the closest ports on the Mediterranean Sea and a starting place for many asylum seekers hoping to travel north and west through the Balkans and other European nations.

Around 6,500 refugees from Syria and Iraq were camped out around the Greek town of Idomeni on the Macedonian border, the site of Monday’s disturbance, where authorities are processing only a few dozen people per day to pass through. This has led to a migrant bottleneck that continues to grow daily, with estimates suggesting Greece could host tens of thousands more in the coming weeks if border controls are not loosened.

“We estimate that we will have a number of people trapped in our country which will be between 50,000 and 70,000 ... I believe in the coming month,” said Greek Migration Minister Yannis Mouzalas, according to Reuters. More than 1 million migrants passed through the Hellenic Republic in 2015.

The rush of migrant protesters in Idomeni led to police firing tear gas and stun grenades into the crowd, and several people were nearly trampled in the ensuing struggle, per The Associated Press. Protesters in the area also blocked a rail line and turned back a cargo train, calling for authorities to “open the border.”

While Greece deals with a continuous influx of refugees, other European nations are working to keep their borders closed or are unable to deal with the needs of the thousands of people flowing in. Macedonia, for example, is not letting the migrants through as it waits for its northern neighbors to decide their position on taking in more people.

The start of the intense backup in Greece began more than a week ago, when Austria and other Balkan nations agreed to greatly reduce the migration flow through their borders. This response was met with criticism from groups such as Amnesty International, who say European countries should be doing more to provide for the stranded refugees.

“Tragically, there seems to be more willingness among European countries to coordinate blocking borders than to provide refugees and asylum-seekers with protection and basic services,” Giorgos Kosmopoulos of Amnesty’s Greek operations, told the AP.

In response to the Austrian-led actions, Greece warned that it will block any decision at an upcoming European Union summit if other European nations do not make efforts to share the refugee burden.

“We will not accept the transformation of our country to a permanent warehouse for human beings, while at the same time we continue to operate in Europe and at summit meetings as if nothing is happening,” Greek Prime Minister Alexis Tsipras said last week.

Austrian Vice Chancellor Reinhold Mitterlehner said Monday that his country’s policies “are necessary [and] we're going to maintain them.”

German Chancellor Angela Merkel, a major figure in EU politics and in the German migration debate, called for a more open approach than countries like Austria are moving toward.

“We can't do this in such a way that we simply abandon Greece,” she said Sunday, according to the Associated Press. “This is exactly what I fear: When one country defines its limit, another must suffer. That is not my Europe.”