SALZHEMMENDORF, Germany >> As a volunteer firefighter, Sascha D. was among the crew that rushed to the home of an immigrant family after it was firebombed in this small town in central Germany last summer.

But before he arrived, a court was told this month, Sascha, 25, who is fond of late-night drinking and right-wing metal bands, and a friend, Dennis L., carefully made the Molotov cocktail themselves, using a pen to push wood shavings into the gasoline-filled bottle.

Dennis, 31, who liked to daub swastikas on village walls, then hurled it through a window of the street-level apartment of a 34-year-old single mother of three from Zimbabwe who remains so traumatized she still has trouble sleeping, the court heard. German law protects the identity of the accused, meaning that unless there are extenuating circumstances, only first names and initials of surnames are made public.

“If the Negro burns, I will really celebrate,” Dennis said afterward, according to Saskia B., 24, who served as the driver for the two but is now testifying against her friends.

Dennis denies he made the remark about an attack that did not injure anyone because the room hit was, by good fortune, empty that night. But little else seems disputed in the trial of the three friends on attempted murder charges, a rare prosecution against one of almost 1,200 attacks on refugee shelters — including some 100 arsons — since January 2015.

In fact, what made the attack in this impoverished town of 9,000, about 25 miles southwest of Hanover, exceptional is that the culprits were quickly caught and confessed — even as assaults on refugee shelters have become routine, averaging more than two a day since the start of last year.

As Germany struggles to absorb more than 1 million refugees, the attacks present an increasingly pressing challenge for Chancellor Angela Merkel and local authorities, who face a sudden and sinister rise in right-wing racism, tinged with Nazi ideas.

So far, the record of law enforcement has been spotty, as such cases are left in the hands of the overstretched local authorities under Germany’s diffuse federal system, which does not have a national hate crime statute.

“The deeds are usually committed at night and on the weekend,” Frank Neubacher, a professor at the Institute for Criminology at Cologne University, noted in an email. “Impartial witnesses often do not exist, and the perpetrators leave little trace.”

But more hostility toward refugees since the start of a year that began with sexual assaults linked to migrants in Cologne has also hardly discouraged the arsons, the latest of which occurred early Sunday in the Saxon town of Bautzen. There, a drunken crowd cheered as a hotel that had been converted into a refugee shelter burned, and tried to obstruct firefighters from dousing the flames. No one has been arrested.

The arson attacks have become a German specialty. Just a few such attacks have been recorded in Sweden, and not one in neighboring Austria, despite a similar percentage of new migrants, and a far-right party polling 30 percent or more.

In Germany, the pattern of accelerating violence, experts say, coincides with the emergence of the anti-Islam, anti-immigration group Pegida since late 2014.

“Quite new right-wing extremist groups have long been building on the Internet,” said Andreas Zick, a professor at Bielefeld University who heads its Institute for Interdisciplinary Research Into Conflict and Violence. “The readiness to approve and use violence has gotten stronger and stronger in the last two years.”

In Germany, but also in other countries in Europe, “parallel societies are being formed,” and are taking power into their own hands, he said.

Studies by Zick’s institute suggest that 20 percent of the population is susceptible to what he depicted as a new nationalist populism, with many citizens shifting far to the right as they feel increasingly powerless and lose faith in politicians and the news media.

A vocal minority nationwide is protesting outside shelters, especially in the east, and committing more assaults on the refugee housing — 118 attacks in the first six weeks of this year, the Interior Ministry says.

In addition, German authorities are noticing a destructive trend: the flooding of refugee homes newly renovated at public expense.

Turning on the taps is unlikely to cause injury or even death, as arson might, but is just as certain to cause hundreds of thousands of dollars’ worth of damage and to keep migrants from being moved in.

The first arson case to gain attention nationwide occurred in the northern Bavarian village of Vorra in December 2014, when someone set fire to a renovated shelter that was about to receive 40 refugees. Almost a year later, four refugee families moved into the re-renovated property. But no one was ever arrested for the fire.

Tracking anti-immigrant attacks is difficult, in part because of Germany’s splintered federal system. But the Amadeu Antonio Foundation, a respected nongovernment source, compiles lists culled from news media and police reports nationwide.

During the week of Jan. 24, for instance, it found 10 suspected racist or right-wing assaults, including an arson on Jan. 25 that damaged two houses intended for 25 asylum seekers in Witten, in North Rhine-Westphalia.

The trial of Dennis and his friends, which is taking place in the city of Hanover, has similarly exposed a worrying attraction to far-right ideas.

The men were said in court to have been among the members of an online chat room known as Swastika Garage.

Several witnesses testified that a favorite pastime for the two men was drinking heavily and listening to right-wing rock bands, including at least one, Landser, that was outlawed in 2003 for inciting hatred.

Clemens Pommerening, the mayor of Salzhemmendorf, said he was shocked the night of Aug. 27-28 when he was informed of the attack on the Zimbabwean family. The mother and her three children, the only Africans in town, had arrived here in November 2014.

“I wouldn’t imagine anyone doing this,” Pommerening, 48, said in his tidy office in the town shopping center. “But now, of course, I can’t exclude it. And if it can happen here, it can happen anywhere.”

He takes comfort in the fact that some 2,000 people showed up for a pro-refugee rally the evening after the firebombing and about 120 refugees still live in the town.

Before the trial opened, Roman von Alvensleben, the main defense lawyer for Dennis, said he hoped that the town would not be stigmatized for what he depicted as one night’s drunken folly by three misguided people.

“My client is really a person you can look at and think, he cannot have done it,” he said.

In court, however, Saskia, the driver, suggested that her two friends had acted consciously, even if they were drunk, though her own credibility was called into question.

Though Saskia, a single mother of two, said she had no idea what a Molotov cocktail was, it emerged in court that her mother had sent her a message on WhatsApp after the attack asking, “Did you throw a Moli?” with a smiley face attached.

Perhaps the most striking court appearance was by the victim, whom her lawyer, Sebastian Piontek, asked be identified only by her first name, Margaret.

Speaking hesitantly through a translator, she described how she and her children awoke to the bangs and shouts of firefighters, then escaped through a living room window.

To this day, she said, she cannot sleep and is undergoing therapy. Her frightened children always sleep with her now. She wept when shown pictures of her charred former home.

Although Pommerening said a new apartment had been found for her and her children, the family moved this month to a larger nearby town, Hameln.

During the proceedings, Tanja Brettschneider, a lawyer for Dennis, said her client wanted to apologize and asked if Margaret would accept.

The victim paused, then said simply: “Must I answer that?”