NEW DELHI — Rahis Mohammed's voice shook as he described how a mob of 200 people arrived in his neighborhood intent on destruction while calls to the police went unanswered.

Standing on a deserted road dotted with charred vehicles Wednesday, he watched as a police car passed. “After 48 hours they have come,” Mohammed, 40, said bitterly. “They left us to die.”

As India’s capital reels from an outbreak of communal violence that has left nearly 40 people dead and 200 injured, criticism of the response by law enforcement authorities is growing.

Witnesses say police were unwilling or unable to control the mobs and, in some instances, may have participated in the worst riots in New Delhi in decades.

At least one police officer is among those killed in the violence. The Delhi Police rejected accusations that its response was slow or inadequate and denied allegations that officers encouraged rioters and beat residents. Others accused the police of shooting indiscriminately.

By Thursday, the violence in neighborhoods of northeastern Delhi had subsided. Television channels showed a senior police officer walking the streets of one riot-hit area wearing riot gear and a helmet, urging people to come out of their homes and return to daily life.

The violence came after months of protests over a controversial citizenship law enacted by the government of Prime Minister Narendra Modi. The law has intensified fears among India’s 200 million Muslims that Modi’s goal is to marginalize them and turn India into a Hindu nation.

Critics say the law, which excludes Muslim migrants from a fast track to citizenship, runs counter to India’s secular ethos. Supporters of the law say it helps persecuted religious minorities from nearby countries. Members of Modi’s party have vilified the protesters, likening them to traitors and criminals.

This week, those tensions boiled over, triggered by a politician in Modi’s party who threatened to remove protesters holding a sit-in in northeastern Delhi. Clashes broke out late Sunday and devolved into deadly violence throughout Monday and Tuesday, including during President Trump’s visit to the city.

It is not clear whether Trump’s presence in Delhi and the attendant security demands affected the police’s ability to respond to the riots. One news report suggested that the police had informed the government that they were short of personnel to control the violence. India’s Ministry of Home Affairs denied the report, saying that adequate forces were in place. The police force in India’s capital is controlled by the central government.

Vikram Singh, a former senior police official in India’s largest state, Uttar Pradesh, said the fact that authorities had not arrested the politician who helped spur the violence spoke of interference by the governing Bharatiya Janata Party. The law should be “unsparing,” he said, not dictated by political whims.

The Delhi Police was already facing accusations of brutality and partisanship before this week’s violence. In December, police stormed a university, beating unarmed students and firing tear gas into a library during a protest of the citizenship law. Meanwhile, authorities have not made any arrests in assaults against students at a different university. The perpetrators allegedly are associated with the governing party.

This week’s failures are seen as far more grave. Member of Parliament Naresh Gujral wrote to the home ministry castigating the police for inaction, New Delhi Television reported. Gujral said that he had called police asking them to help 16 Muslims trapped in a house Wednesday night as a mob tried to break in. No police went to the scene. Instead, those trapped were ultimately rescued by their Hindu neighbors, he said.

A senior judge in Delhi also criticized the city’s police as failing to take steps to arrest the rioters or those inciting violence through hate speech.

“How many more lives have to be lost? How much property has to be destroyed?” said Justice S. Muralidhar on Wednesday, expressing “anguish” at the situation, according to a report in Bar & Bench, an Indian legal publication. Hours later, the government issued a transfer order for the judge that lawyers described as highly unusual.

On Thursday, the U.S. State Department extended its sympathies to the families of the dead and injured. “We urge all parties to maintain peace, refrain from violence, and respect the right of peaceful assembly,” it said.

At Delhi’s Guru Teg Bahadur Hospital, bereaved families waited to claim the bodies of relatives killed in the violence. Muslims sat in one corner while Hindu families sat at a distance in an unspoken religious separation. Relatives wept and accused the police of complicity.

Waris Ali was waiting for the body of his nephew Mohsin Ali, who was 24 and newly married. Mohsin Ali had left his job at a shop and was heading home when he called colleagues to tell them that mobs were on the road. They did not hear from him again. After a frantic search, his uncle said, the family discovered his body at the hospital with head injuries.

Niha Masih and Tania Dutta contributed to this report.