BERLIN — Thousands of volunteers have heeded calls to help the stream of migrants arriving in Europe in recent days, cheering them at train stations in Austria and Germany and showering them with food, drinks and toys.

But signs of tension have continued to appear this week, even in the most welcoming countries, reflecting fear, misunderstanding or racism as the Continent struggles to cope with an influx of tens of thousands of people.

On Tuesday (Sept 8), a journalist in Hungary was seen on camera deliberately tripping a migrant carrying a child through a field. Yesterday, the authorities in Germany reported yet another suspected arson attack on a refugee shelter, and migrants trying to cross Denmark said the police there had physically forced them onto buses.

The police in Denmark said scuffles had broken out between officers and groups of migrants at the bus station in Padborg, just across the border with Germany, where some migrants had staged a sit-in after being taken off trains and blocked from continuing their journey to Sweden.

Since a centre-right government took over in Denmark this year, the country has cut assistance benefits for refugees by half — a fact the government sought to make clear by taking out advertisements in a newspaper in Lebanon, where hundreds of thousands of Syrian refugees have fled. As a result, some migrants who declined to apply for asylum in Germany have sought to pass through Denmark in hopes of pressing farther north to Sweden or Norway.

Two boys from Darfur, Sudan, Ali Eissa, 16, and his friend Ahmad Adam, 15, were among a group of about 200 migrants who stormed out of a migrant reception centre in a former school in the Danish town of Padborg, determined to walk the roughly 300 miles to Sweden after having been removed from a train bound for Malmo, Sweden, and told to apply for asylum or return to Germany.

"We are going to Sweden," Ali said. When told it was very far, he replied, "No problem, we can go."

Ali said he was stunned by the hostility of the Danish police, including some who had pushed people trying to march onto buses after officers in Germany had allowed them to leave that country.

Ms Helle Lundberg, a spokeswoman for the police in the South Jutland region, said the tensions had been caused by officers trying to enforce a "safety situation", but she said they were enforcing Danish and European laws prohibiting anyone without valid travel documents from leaving the country, except to return to where they had come from.

The police were forced to close the main highway running north from the German border later yesterday, after migrants refused to leave. Journalists were banned from the highway, and a no-fly zone was put in place above it, on the grounds that helicopters and low-flying planes would "scare those marching", the police said.

Denmark's national railway, DSB, said it had stopped all train travel between Denmark and Germany following a police request. Ms Lundberg said it was a safety measure to prevent those blocking the railway station from being harmed.

As the tensions in southern Denmark grew, the country's justice minister, Soren Pind — whose Facebook page featured an image of John Wayne from "Rio Bravo" — cut short a trip to the United States yesterday to return home, posting that the situation demanded his presence.

Chancellor Angela Merkel of Germany yesterday repeated her denunciation of far-right violence against migrants in a speech to Parliament, even as the police reported another suspected arson attack on a shelter overnight.

The police in the western state of Saarland said a fire broke out early yesterday in a former school that was being converted to take in dozens of migrants. It was the third blaze in a shelter this week, although the police have said that they believe one was caused by a faulty wire. German authorities have recorded more than 200 attacks targeting facilities for asylum seekers or against individuals in the first half of the year.

Many Germans have been outraged by the violence in their country, helping spur the outpouring of generosity that has been seen over the past week.

In Hungary on Tuesday, a video captured a Hungarian camerawoman, identified as Ms Petra Laszlo, kicking a migrant fleeing from the police in a field near the border with Serbia where many migrants cross. The N1TV Internet television channel, which works to popularise the anti-immigrant Jobbik party, said yesterday in a statement that Ms Laszlo had been fired for behaving in "an unacceptable manner".

By late yesterday, a "Petra Laszlo Shame Wall" on Facebook had garnered support from more than 22,000 people decrying her actions.

"There are many people like Petra Laszlo," organisers wrote. "This time what she has done has been caught on camera. But often, these acts remain silent." THE NEW YORK TIMES