NEW DELHI: At least 32 people have been killed in the deadliest violence to engulf India's capital New Delhi for decades as a heavy deployment of security forces brought an uneasy calm on Thursday, a police official said.

The violence began over a disputed new citizenship law on Monday but led to clashes between Muslims and Hindus in which hundreds were injured. Many suffered gunshot wounds, while arson, looting and stone-throwing has also taken place.

"The death count is now at 32," Delhi police spokesman Anil Mittal said, adding the "entire area is peaceful now."

At the heart of the unrest is a citizenship law which makes it easier for non-Muslims from some neighbouring Muslim-dominated countries to gain Indian citizenship.

UN human rights chief Michelle Bachelet said the new law adopted last December is of "great concern" and she was worried by reports of police inaction in the face of assaults against Muslims by other groups.

"I appeal to all political leaders to prevent violence," Bachelet said in a speech to the UN Human Rights Council in Geneva.

Critics say the law is biased against Muslims and undermines India's secular constitution.

Prime Minister Narendra Modi's Hindu nationalist Bharatiya Janata Party has denied having any prejudice against India's 180 million Muslims, saying that law is required to help persecuted minorities.

New Delhi has been the epicentre for protests against the new law, with students and large sections of the Muslim community leading the protests.

As the wounded were brought to hospitals on Thursday, the focus shifted on the overnight transfer of Justice S. Muralidhar, a Delhi High Court judge who was hearing a petition into the riots and had criticized government and police inaction on Wednesday.

Law minister Ravi Shankar Prasad said the transfer was routine and had been recommended by the Supreme Court collegium earlier this month.

Opposition Congress party leader Manish Tiwari said every lawyer and judge in India should strongly protest what he called a crude attempt to intimidate the judiciary.

Information and Broadcasting Minister Prakash Javadekar said inflammatory speeches at the protests over the new citizenship law in the last few months and the tacit support of some opposition leaders was behind the violence.

"The investigation is on," he said.

Prime Minister Narendra Modi, who romped to re-election last May, also withdrew Jammu and Kashmir's autonomy in August with the objective of tightening New Delhi's grip on the restive region, which is also claimed by full by Pakistan.

For months the government imposed severe restrictions in Kashmir including cutting telephone and internet lines, while keeping hundreds of people, including mainstream political leaders, in custody for fear that they could whip up mass protests. Some restrictions have since been eased.

Bachelet said the Indian government continued to impose excessive restrictions on the use of social media in the region, even though some political leaders have been released, and ordinary life may be returning to normal in some respects.