Hundreds of migrants and refugees stranded in Serbia have set off on foot from the capital Belgrade towards the closed Hungarian border.
Police escorted them as they chanted, '"Open the border! Open the border, Hungary!"
Some carried banners, one of them reading, "We are people, not animals."
Nearly 7,000 migrants and refugees, most fleeing war and poverty in Syria, Iraq and Afghanistan, are trapped in Serbia.
They have been prevented from continuing further into Europe by fences now running the length of the Hungarian-Serbian border.
A man from Pakistan named Farad, among those walking, says he has walked to the Hungarian border 10 times in the past two months.
"I go to border because border is closed and I have been two months here and I have 10 times walked to border (inaudible). So, today, all people go to border, because I am appealing for Hungary open the border please."
Hungary has not accepted the migrants and refugees the European Union is trying to relocate from Italy and Greece.
The country's prime minister, Viktor Orban, is proposing a constitutional amendment that would ban the mass settlement of people without parliament's approval.
He says it would reflect the wishes of voters who, in a weekend referendum, overwhelmingly approved the government's stance against the EU's mandatory quotas.
"We have to say clearly that we ban mandatory mass settlements. We have to make it clear that this is a question of sovereignty and that no decision in Brussels can call into question Hungary's inalienable right of disposal on matters of territorial integrity and its population."
Less than half of the Hungarian electorate voted in the referendum, though, rendering the results officially invalid.
The flow of migrants and refugees elsewhere in Europe is not easing.
In Italy, more than 200 migrants, including children travelling alone, were brought ashore yesterday after being rescued in the Mediterranean Sea.
About 6,000 had been rescued and 22 found dead on the maritime route from North Africa on Monday.
The International Organisation for Migration says more than 130,000 migrants and refugees have arrived in Italy since the start of the year.
Speaking in Brussels, United States secretary of state John Kerry says the approach of some European leaders to the crisis has been admirable.
He warns, though, that, ultimately, ending the conflicts many are fleeing will be the only long-lasting resolution.
"Ending the war in Syria is imperative for many reasons, including the need to reduce the flow, or ease the flow, into Europe of migrants and refugees.
"To some, formulating the right response to refugees is as easy as putting up a green light or a red one -- they just think it's simple," he said.
"But, in fact, the problem, as you know, has many dimensions, related to legal responsibilities, resources, security, safe transit, human trafficking, gender abuse and the special needs of children.
"Ultimately, however, the only fully satisfactory solution to the refugee dilemma is to stop the wars."
