The police in Milwaukee on Monday were investigating an attack on a Hispanic man as a possible hate crime after the victim, who was severely burned on his face and neck, reported that his attacker threw acid on him and told him to “go back to your country.”

The victim, Mahud Villalaz, 42, was assaulted outside a Mexican restaurant in the Lincoln Village neighborhood of Milwaukee on Friday. He described being attacked by a white man who hurled racist insults at him and accused him of being an “illegal” before splashing acid on him.

The police said they had arrested a 61-year-old white man in connection with the attack, but as of Monday night they had not announced any charges nor released the suspect’s identity.

Mr. Villalaz, an American citizen who came to the United States from Peru 19 years ago, said the episode began when he parked near the taqueria and was confronted by the man about how close his pickup truck was to a bus stop. Mr. Villalaz returned to his vehicle and moved it about a block away. As he walked toward the restaurant again, he said, the man said, “You came here to invade.”

Mr. Villalaz said he rushed into the restaurant’s bathroom and rinsed his face with water, which may have lessened his injuries. The police described the liquid only as a “corrosive substance,” though Mr. Villalaz said doctors told him they thought it was battery acid and it also burned a jacket, sweater and shirt he was wearing.

Mayor Tom Barrett of Milwaukee and members of the city’s Hispanic community said they were alarmed by the attack and were worried that statements made by President Trump had cultivated an anti-immigrant sentiment.

“This anger towards people from other countries is being fed by our president and by his followers,” Mr. Barrett, a Democrat, told reporters on Monday. “What we saw over the weekend is a manifestation of that anger.”

“The victim is a United States citizen,” Mr. Barrett added. “He has as much right to be here as any one of us.”

Darryl Morin, the president of Forward Latino, an advocacy group based in the Milwaukee area, said, “Sadly this is following the pattern we’re seeing nationwide,” citing the mass shooting in which Hispanics were targeted in El Paso, Texas, as the most horrifying example.

The attacker’s reported use of the word “invade” was particularly troubling, Mr. Morin said, given Mr. Trump’s public warnings of an “invasion” by immigrants on America’s southwestern border — language also echoed by the El Paso suspect. Mr. Trump also told a group of four minority Democratic congresswomen to “go back” to their countries this summer.

“What we are seeing is not just an attack on immigrants, it’s an attack on all Hispanics,” Mr. Morin said. “It’s an attack on America as a whole.”

According to José G. Pérez, who represents Lincoln Village and seven nearby neighborhoods on the City Council, the area around the attack is overwhelmingly Hispanic and has been attracting new businesses.

“Latinos are the backbone of population growth in the city and in the district,” he said.

Mr. Villalaz was treated at a hospital for second-degree burns on his face and third-degree burns on his neck, as well as irritation to his left eye. He was recovering at home on Monday.

Mr. Morin, whose organization has been providing assistance to Mr. Villalaz, said the victim and his family were comforted somewhat by the arrest of a suspect, and grateful for the efforts of the Milwaukee Police Department. An online campaign to raise funds for Mr. Villalaz’s medical expenses has already exceeded its goal of $15,000.

Mr. Villalaz, the father of two young boys — Alain, 7, and Aayden, 5 — said the attack had been hard on his sons. “The younger one started crying and said, ‘Why would somebody do this to you, Daddy, when you did nothing to him?’” he said. “How do you explain this to a little boy?”

“But my older son understands a little better. He said, ‘It was crazy people out there.’”

Amy Osorio contributed reporting.