The chief minister of India's Uttar Pradesh state has rebuffed accusations from rights groups of police abuses during protests against a new citizenship law, crediting his tough stand with restoring calm to the streets.

The northern state has seen the most violent turmoil over Prime Minister Narendra Modi's citizenship law. Activists say the law is discriminatory toward the Muslim community, which makes up some 14 per cent of India's population.

Out of at least 25 people who have been killed since the protests began this month, 19 were in Uttar Pradesh (UP), India's most populous state. The clashes in the state appear to have eased over the past week, however, though small-scale demonstrations continue.

The state's chief minister, Yogi Adityanath, a hardline Hindu priest who belongs to Modi's Hindu nationalist party, said his tough policies had ended the trouble.

"Every rioter is shocked. Every troublemaker is astonished. Looking at the strictness of the Yogi government, everyone is silent," one of Adityanath's said on one of his verified Twitter accounts late on Friday. "Do whatever you want to, but the damages will be paid by those who cause damages."

Last week, his government said it was demanding millions of rupees from more than 200 people, threatening to confiscate their property to pay for damage during the protests.

'Excessive force'

Rights groups have decried what they say have been mass detentions and excessive force in the state, where officers have arrested more than 1,000 people. The citizenship legislation makes it easier for members of religious minorities from India's Muslim-majority neighbours — Afghanistan, Bangladesh and Pakistan — who settled in India before 2015 get citizenship but does not offer the same concession to Muslims.

Critics say the law — and plans for a national citizenship register — discriminate against Muslims and are an attack on the secular constitution by Modi's government. The government has said no citizen will be affected and there is no imminent plan for a register.

Later on Saturday, the general secretary of the opposition Congress party, Priyanka Gandhi Vadra, added to criticism of UP police. Vadra told reporters she was in a group driving to the home of a former police officer arrested in connection with the protests when a police vehicle blocked the way, so Vadra decided to continue on foot.

"(Police officers) encircled me, strangulated me, grabbed me … and pushed me. I fell," Vadra said. "I took a two-wheeler. They stopped me again and then I came here by walking."

A vegetable vendor pushes his cart past police personnel standing guard on a street in Lucknow, Uttar Pradesh, Friday. Paramilitary and police forces were deployed and the internet shut down in Muslim-majority districts where more than a dozen people have been killed and more than 1,000 people arrested in protests. (Rajesh Kumar Singh/The Associated Press)

Lucknow's Senior Superintendent of Police Kalanidhi Naithani later released a video saying an officer involved in the incident had submitted a report denying Vadra's allegations.

A video circulating on social media is likely to compound the concerns of those worried about the plight of Muslims. It shows a senior UP police officer telling a demonstrator to "go to Pakistan if you don't want to live here."

The official, Akhilesh Narayan Singh, told Reuters that some protesters had been shouting pro-Pakistan slogans. "It is in this situation I told them to go to Pakistan," he said.

Congress party officials led protests on Saturday under the slogan "Save Constitution-Save India."

Meanwhile, Hindu activists linked to Modi's party conducted workshops in slums in an effort to ease public discontent.