Chief US diplomat for South Asian affairs, Alice Wells, in a mildly worded statement on Thursday urged those behind the recent communal unrest in India's capital to "refrain from violence".

In a tweet, she said: "Our hearts go out to the families of the deceased and injured in New Delhi. We echo PM @NarendraModi’s call for calm and normalcy and urge all parties to maintain peace, refrain from violence, and respect the right of peaceful assembly."

Protests against a contentious citizenship law began on a smaller scale on Sunday but escalated on Monday — as US President Donald Trump started his two-day trip to India — and Tuesday into running battles between Hindus and Muslims in New Delhi’s north-east, where rioters armed with stones, swords and even guns were out in force.

Sporadic violence hit parts of Delhi overnight as gangs roamed streets littered with the debris of days of communal riots that have killed 32 people, police said on Thursday.

India accuses US commission of politicising violence

Wells' remarks come after India on Thursday accused a US government commission of politicising communal violence in New Delhi that killed at least 32 people and injured more than 200.

On Wednesday, the US Commission on International Religious Freedom said it was deeply troubled by the violence and cited accounts that police had not intervened in attacks against Muslims, which police and India's federal government have denied.

"The government is failing in its duty to protect its citizens," Commissioner Anurima Bhargava said.

India's External Affairs Ministry said the commission's comments were "factually inaccurate and misleading" and appeared to be "aimed at politicising the issue".

On Thursday, burnt shops and public vehicles stood charred near a highway in Chandbagh, a Muslim-dominated locality. Streets were littered with broken glass and charred petrol bombs as dozens of police in camouflage and helmets patrolled.

Several reports by Indian media outlets said Muslim localities in the Indian capital were attacked by Hindu mobs screaming pro-Hindu slogans. The reports said these mobs rioted with impunity as the police appeared to aid the marauding crowds.

Muslim rioters, too, have been violent, and a number of Hindus, including security personnel, are among the dead and injured.

Most of the violence, however, appeared to be targeting Muslims who complained that while Hindu mobs went on a rampage, the police went missing. Police have denied the allegations.

Hours before the violence first began on Sunday, local politician Kapil Mishra, who is affiliated with Prime Minister Narendra Modi's Bharatiya Janata Party, appeared at a rally against the citizenship law's opponents and issued an ultimatum to the police to clear out the demonstrators. He told the crowd at the rally if police wouldn't clear out the demonstrators, he and his followers would do it themselves.

Many people, including Hindus, believe Mishra and his Hindu nationalist supporters stoked the latest riots.

The contentious law that was passed in December fast-tracks naturalisation for foreign-born religious minorities of all major faiths in South Asia except Islam. Nationwide protests followed, with many opponents saying the law is discriminatory and breaks from India's secular traditions.

The supporters of the law, including leaders from Modi's party, have often called the protests anti-Indians funded by the state's enemies.

Trump's first state visit to India included a lavish reception in Modi's home state of Gujarat and talks with the Indian leader, but the US leader said they didn't discuss the violence. Trump declined to comment about the citizenship law, saying he wanted to leave that to India, before departing.

OIC condemns violence against Muslims

Meanwhile, the Organisation of Islamic Cooperation (OIC) has condemned the recent and "alarming" violence against Muslims in India.

In a tweet, the body said: "OIC condemns the recent & alarming violence against Muslims in India, resulting in the death & injury of innocent people & the arson and vandalism of mosques and Muslim-owned properties. It expresses its sincere condolences to the families of the victims of these heinous acts."

The OIC called on Indian authorities to bring the instigators and perpetrators of the acts of anti-Muslim violence and to ensure the safety of all the country's Muslim citizens as well as Islamic holy sites across India.