(CNN) A trash-strewn field along the Hungarian-Serbian border served as the latest flashpoint in Europe's migrant crisis Monday as people grew weary of waiting for days in primitive conditions to resume their journey to safety.

The question on all their lips: "Why are they treating us like this?"

At times, the migrants -- most of them from Iraq, Syria and Afghanistan -- tussled with police blocking a road from this holding site to a transit camp near Roszke, Hungary, where they can register as refugees and continue their journeys.

Buses were carrying small numbers of migrants to the camp, but many have been forced to wait at the holding site for as many as three days with little in the way of services or support.

One Hungarian nonprofit was on site handing out biscuits, fruit and water, and a medical tent was erected Monday.

Only handful of buses.Ppl fed up waiting among the trash."We will walk 2 camp & register,it's 10mins away." #hungary pic.twitter.com/NMZuipw9hb — Arwa Damon (@arwaCNN) September 7, 2015

Meanwhile, Austria and Germany warned they can't keep up with the influx of refugees and said they must begin to slow the pace.

JUST WATCHED Migrants determined to enter Austria, Germany Replay More Videos ... MUST WATCH Migrants determined to enter Austria, Germany 02:29

More than 16,000 migrants have streamed into Austria since Saturday, Burgenland state police spokesman Wolfgang Bachkoenig said Monday. Virtually all continued to Germany, where the city of Munich had received more than 17,500 people, police said.

"We must now, step by step, go from emergency measures to a normality that is humane and complies with the law," Austrian Chancellor Werner Faymann said.

At least 2,800 have died or disappeared during the journey. Those who make the crossing face uncertain futures in European nations, which differ in their approach to asylum seekers.

Some European nations offer help; Denmark tightens restrictions

On Monday, German Chancellor Angela Merkel said her country would pledge an additional €3 billion to the migrant crisis. She said Germany "is of course willing to accept more refugees," but called on other European countries to take in more.

Moments after Merkel spoke, French President Francois Hollande said France is ready to take on more responsibility.

He said the European Commission will propose distributing 120,000 refugees over the next two years, of whom France would take in 24,000.

"We will do so because it is the principle to which France is committed," Hollande said.

And Britain will take up to 20,000 Syrian refugees over the next five years, Prime Minister David Cameron said Monday. But the country will focus on resettling refugees from camps in countries bordering Syria, not those who have already entered Europe.

"This provides refugees with a more direct and safe route to the United Kingdom rather than risking the hazardous journey to Europe, which has tragically cost so many lives."

Refugees will receive a five-year humanitarian protection visa, he said.

Not every European country is opening its arms.

Denmark, for instance, paid for ads in Arabic in four Lebanese newspapers to get the word out about its own new, tightened restrictions -- such as reducing social benefits -- to try to prevent refugees from getting into the Scandinavian nation.

"We cannot simply keep up with the present flow," Immigration and Integration Minister Inger Stojberg, a member of the right-wing Venstre Party, said on Facebook. "In light of the huge influx to Europe these days, there is good reason for us to tighten rules and get that effectively communicated."

'We went through a torture'

Many of the migrants arrive with harrowing tales of crossing the Mediterranean, then walking from Greece through Macedonia, Serbia, Hungary and finally into Austria.

Austria's border with Hungary remains open to potential refugees, Austrian Interior Ministry spokesman Alexander Marakovits said Sunday, as packed buses and trains continued to arrive.

Many Austrians brought food and water and cheered for the refugees pouring onto the platform at Vienna's train station.

JUST WATCHED Austrians give food, water, train tickets to migrants Replay More Videos ... MUST WATCH Austrians give food, water, train tickets to migrants 01:52

One man who recently arrived in Austria talked of the family's difficult journey through Hungary.

"We went through a torture," he said, standing next to his two daughters. "We walked 110 kilometers (70 miles) with the children. They didn't allow us to take cars or trains."

But he said the Hungarian people "were very nice" and the situation got better when the family arrived in Austria.

"We are comfortable here, and we like the people and the government of Austria."

Of the thousands who arrived in Austria this weekend, a dozen or so have opted to apply for asylum there, the country's Interior Ministry said. Many want to go farther, particularly to Germany.

Attacks against refugees on the rise

But the dangers don't stop once refugees reach Germany.

JUST WATCHED Thousands of migrants arrive in Germany Replay More Videos ... MUST WATCH Thousands of migrants arrive in Germany 02:13

At least 340 attacks have taken place on refugee camps in Germany this year, the Interior Ministry said. Most of the incidents are believed to be fueled by radical right-wing, anti-immigrant sentiment.

The attacks include vandalism, hate speech and arson, as well as violent attacks on people. At least 38 violent assaults have been recorded this year, up from 28 last year.

On Monday, another suspicious fire broke out at a house for asylum seekers in Rottenburg am Neckar, police said.

Five people were injured -- three by smoke inhalation and two by jumping out of the building's first and second floors. None of the rooms is inhabitable anymore.

The cause is under investigation.

Border control

Photos: Europe's migration crisis in 25 photos Photos: Europe's migration crisis in 25 photos A woman cries after being rescued in the Mediterranean Sea about 15 miles north of Sabratha, Libya, on July 25, 2017. More than 6,600 migrants and refugees entered Europe by sea in January 2018, according to the UN migration agency , and more than 240 people died on the Mediterranean Sea during that month. Hide Caption 1 of 26 Photos: Europe's migration crisis in 25 photos Refugees and migrants get off a fishing boat at the Greek island of Lesbos after crossing the Aegean Sea from Turkey in October 2015. Hide Caption 2 of 26 Photos: Europe's migration crisis in 25 photos Hide Caption 3 of 26 Photos: Europe's migration crisis in 25 photos Migrants step over dead bodies while being rescued in the Mediterranean Sea, off the coast of Libya in October 2016. Agence France-Presse photographer Aris Messinis was on a Spanish rescue boat that encountered several crowded migrant boats. Messinis said the rescuers counted 29 dead bodies -- 10 men and 19 women, all between 20 and 30 years old. "I've (seen) in my career a lot of death," he said. "I cover war zones, conflict and everything. I see a lot of death and suffering, but this is something different. Completely different." Hide Caption 4 of 26 Photos: Europe's migration crisis in 25 photos Authorities stand near the body of 2-year-old Alan Kurdi on the shore of Bodrum, Turkey, in September 2015. Alan, his brother and their mother drowned while fleeing Syria. This photo was shared around the world, often with a Turkish hashtag that means "Flotsam of Humanity." Hide Caption 5 of 26 Photos: Europe's migration crisis in 25 photos Migrants board a train at Keleti station in Budapest, Hungary, after the station was reopened in September 2015. Hide Caption 6 of 26 Photos: Europe's migration crisis in 25 photos Children cry as migrants in Greece try to break through a police cordon to cross into Macedonia in August 2015. Thousands of migrants -- most of them fleeing Syria's bitter conflict -- were stranded in a no-man's land on the border. Hide Caption 7 of 26 Photos: Europe's migration crisis in 25 photos The Kusadasi Ilgun, a sunken 20-foot boat, lies in waters off the Greek island of Samos in November 2016. Hide Caption 8 of 26 Photos: Europe's migration crisis in 25 photos Migrants bathe outside near a makeshift shelter in an abandoned warehouse in Subotica, Serbia, in January 2017. Hide Caption 9 of 26 Photos: Europe's migration crisis in 25 photos A police officer in Calais, France, tries to prevent migrants from heading for the Channel Tunnel to England in June 2015. Hide Caption 10 of 26 Photos: Europe's migration crisis in 25 photos A migrant walks past a burning shack in the southern part of the "Jungle" migrant camp in Calais, France, in March 2016. Part of the camp was being demolished -- and the inhabitants relocated -- in response to unsanitary conditions at the site. Hide Caption 11 of 26 Photos: Europe's migration crisis in 25 photos Migrants stumble as they cross a river north of Idomeni, Greece, attempting to reach Macedonia on a route that would bypass the border-control fence in March 2016. Hide Caption 12 of 26 Photos: Europe's migration crisis in 25 photos In September 2015, an excavator dumps life vests that were previously used by migrants on the Greek island of Lesbos. Hide Caption 13 of 26 Photos: Europe's migration crisis in 25 photos The Turkish coast guard helps refugees near Aydin, Turkey, after their boat toppled en route to Greece in January 2016. Hide Caption 14 of 26 Photos: Europe's migration crisis in 25 photos A woman sits with children around a fire at the northern Greek border point of Idomeni in March 2016. Hide Caption 15 of 26 Photos: Europe's migration crisis in 25 photos A column of migrants moves along a path between farm fields in Rigonce, Slovenia, in October 2015. Hide Caption 16 of 26 Photos: Europe's migration crisis in 25 photos A ship crowded with migrants flips onto its side in May 2016 as an Italian navy ship approaches off the coach of Libya. Passengers had rushed to the port side, a shift in weight that proved too much. Five people died and more than 500 were rescued. Hide Caption 17 of 26 Photos: Europe's migration crisis in 25 photos Refugees break through a barbed-wire fence on the Greece-Macedonia border in February 2016, as tensions boiled over regarding new travel restrictions into Europe. Hide Caption 18 of 26 Photos: Europe's migration crisis in 25 photos Policemen try to disperse hundreds of migrants by spraying them with fire extinguishers during a registration procedure in Kos, Greece, in August 2015. Hide Caption 19 of 26 Photos: Europe's migration crisis in 25 photos A member of the humanitarian organization Sea-Watch holds a migrant baby who drowned following the capsizing of a boat off Libya in May 2016. Hide Caption 20 of 26 Photos: Europe's migration crisis in 25 photos A migrant in Gevgelija, Macedonia, tries to sneak onto a train bound for Serbia in August 2015. Hide Caption 21 of 26 Photos: Europe's migration crisis in 25 photos Migrants, most of them from Eritrea, jump into the Mediterranean from a crowded wooden boat during a rescue operation about 13 miles north of Sabratha, Libya, in August 2016. Hide Caption 22 of 26 Photos: Europe's migration crisis in 25 photos Refugees rescued off the Libyan coast get their first sight of Sardinia as they sail in the Mediterranean Sea toward Cagliari, Italy, in September 2015. Hide Caption 23 of 26 Photos: Europe's migration crisis in 25 photos Local residents and rescue workers help migrants from the sea after a boat carrying them sank off the island of Rhodes, Greece, in April 2015. Hide Caption 24 of 26 Photos: Europe's migration crisis in 25 photos Investigators in Burgenland, Austria, inspect an abandoned truck that contained the bodies of refugees who died of suffocation in August 2015. The 71 victims -- most likely fleeing war-ravaged Syria -- were 60 men, eight women and three children. Hide Caption 25 of 26 Photos: Europe's migration crisis in 25 photos Syrian refugees sleep on the floor of a train car taking them from Macedonia to the Serbian border in August 2015. How to help the ongoing migrant crisis Hide Caption 26 of 26

European Union countries have an open-border policy that allows the free movement of people between member states. While Germany, France and other countries are opening their doors to more migrants, countries such as Hungary and Austria are clamping down on the flow.

Hungary's right-wing government, trying to stop the flood of migrants, has erected a barbed wire fence along its more than 160-kilometer (100-mile) border with Serbia to prevent them from crossing there. Serbia is not an EU country.

In Austria, the Interior Ministry warned that it is illegal to drive across the border to Hungary, pick up a group of migrants and transport them back to Austria.

But some people are doing exactly that.

JUST WATCHED Volunteers give migrants a lift Replay More Videos ... MUST WATCH Volunteers give migrants a lift 04:18

A group of volunteers from Austria, Germany and Slovakia -- organized on Facebook -- formed a convoy of almost 200 cars to shuttle migrants from the Hungarian border.

"We think that around 380 people came with us," volunteer Erzsebet Szabo said Monday morning. "We are very happy."

Szabo said she's not afraid of getting arrested. After all, she said, even that fate wouldn't compare to what the refugees have endured.

"It's very important that we, altogether, give this big sign that refugees -- the people that need our help and come from the war -- have our solidarity and support."

The disparate responses have resulted in calls from United Nations and European Union officials for European countries to stand shoulder to shoulder in their response to the crisis, the like of which has not been seen since World War II.

"We need concrete, coherent, rational political decisions in the sense of solidarity and responsibility, because European Union was built in decades after the second world war on the experience of that war, that made many of our Europeans flee and leave Europe," EU foreign affairs chief Federica Mogherini told CNN's Christiane Amanpour in an exclusive interview Monday.

"Now we should remember our story and act following the same values and principles that have allowed us to build a continent in peace and prosperity," she said. "We are rich. We are in peace. We have the duty to save and protect people that are fleeing from war."