At least six people were killed and several others injured Friday during violence in the northern Indian state of Uttar Pradesh over the controversial new citizenship law, police said.

"Six people were killed today and we will be sharing details soon," Shirish Chandra, a police official posted in Lucknow said.

According to officials, two people were killed in Bijnor while one each was killed in Sambhal, Firozabad, Meerut and Kanpur.

Protests broke out across many districts in the state during the day despite prohibitory orders imposed by the police.

Uttar Pradesh Police Chief O P Singh said none of the deaths occurred due to police firing.

"We did not fire even a single bullet," Singh was quoted by a local news channel NDTV 24X7 as saying.

On Thursday evening one person was killed in Lucknow, the capital city of Uttar Pradesh. The six deaths on Friday in the state brought the toll to seven in the past 24 hours.

Locals said fresh clashes broke out Friday when police tried to stop them from staging protests against the citizenship law. Police fired tear smoke shells and resorted to baton charging the protesters, who responded by throwing stones.

Violent protests were reported from Firozabad, Bhadohi, Bahraich, Farrukhabad, Gorakhpur, Meerut, Kanpur and Sambhal.

Authorities had already suspended mobile internet services at around a dozen districts, including Aligarh, Mau, Azamgarh, Lucknow, Kanpur, Bareilly, Shahjahanpur, Ghaziabad, Bulandshahr, Sambhal and Allahabad.

Uttar Pradesh Chief Minister Yogi Adityanath Thursday warned that his government will take revenge on those involved in damaging public assets by auctioning their properties to compensate for the loss.

On Thursday two people were killed in similar protests at Mangaluru in the southern state of Karnataka.

Last week four people were killed during protests in the northeastern state of Assam.

Meanwhile, the protests that went on peacefully throughout the day in the capital Delhi turned violent after police stopped people from taking out a march.

Police used water cannons and batons to disperse the protesters, who set ablaze a car near Daryaganj area.

Protests erupted across India and inside universities against the new citizenship law last week after Indian parliament passed the law.

The law aims at granting citizenship to illegal immigrants belonging to six religions - Hinduism, Sikhism, Buddhism, Jainism, Parsi and Christianity - from Bangladesh, Afghanistan and Pakistan. However, it has kept out Muslim immigrants from applying for citizenship.

Opposition parties and civil society members in India criticize the law as contrary to secular principles enshrined in India's constitution as it excludes Muslims.

Political parties, civil society activists and individuals have filed 60 petitions in India's top court to challenge the new law.