Police banned public gatherings in parts of the Indian capital and other cities for a third day and cut internet services to try to stop growing protests against a new citizenship law that have left 14 people dead and more than 4000 detained.

Thousands of protesters stood inside and on the steps of New Delhi's Jama Masijd, one of India's largest mosques, after Friday afternoon prayers.

They waved Indian flags and shouting slogans against the government and the citizenship law – which critics contend marginalises Muslims and threatens India's secular democracy in favour of a Hindu state.

Police banned public gatherings in parts of the Indian capital and other cities for a third day and cut internet services to try to stop growing protests against a new citizenship law that have left 14 people dead and more than 4000 detained. (Sipa USA)

Police banned a proposed march from the mosque to an area near India's Parliament and sprayed protesters with water cannon blasts to prevent them from walking toward a monument about four kilometres away in central Delhi where other protests converged.

The death toll from the protests rose to 14 after Avanish Awasthi, a spokesman for the northern state of Uttar Pradesh, said late Friday that six people had died amid clashes between protesters and police.

Two of the victims were killed in the town of Meerut, when people fired gunshots from a rooftop, said Dinesh Rai, a senior police official in Uttar Pradesh state. He said police did not open fire at the protesters and were investigating the deaths.

Elsewhere in the state, protesters set fire to police posts and vehicles and hurled rocks at security forces. Police fired tear gas and used batons to disperse protesters in the towns of Muzzaffarnagar, Saharanpur, Firozabad and Gorakhpur.

Why people are protesting

Most of the detentions have happened in Uttar Pradesh state, where more than 100 have been arrested and 3305 detained since Thursday, said state police chief O.P. Singh.

Thousands of protesters stood inside and on the steps of New Delhi's Jama Masijd, one of India's largest mosques, after Friday afternoon prayers. (Sipa USA)

Also in New Delhi Friday (local time), about 10,000 people protested outside Jamia Millia Islamia University, the site of weekend clashes in which students accused police of using excessive force that sent dozens to hospitals.

They collected signatures for a petition demanding the new citizenship law to be scrapped.

It allows Hindus, Christians and other religious minorities who are in India illegally but can demonstrate religious persecution in Muslim-majority Bangladesh, Pakistan and Afghanistan a way to obtain Indian citizenship. But the law does not apply to Muslims.

Critics have slammed the law as a violation of the country's secular constitution and label it as the latest effort by Prime Minister Narendra Modi's Hindu nationalist-led government to marginalise India's 200 million Muslims. Mr Modi has defended the law as a humanitarian gesture.

Surveillance video seen by The Associated Press shows police entering Highland Hospital in Mangalore, a southern Indian city, on Thursday night and using batons to disperse protesters who had taken shelter inside.

Also in New Delhi Friday, about 10,000 people protested outside Jamia Millia Islamia University, the site of weekend clashes in which students accused police of using excessive force that sent dozens to hospitals. (EPA)

The video shows two policemen trying to kick open a hospital ward door and some people wearing masks running in a hospital corridor. It earlier shows some protesters throwing rocks at police and then barging into the hospital.

Mohammad Abdullah, a hospital employee, said by phone that police entered the hospital and "fired tear gas shells".

How the protests have unfolded

The protests began last week in the northeastern border state of Assam, the seat of a decades-old movement against migrants, and at predominantly Muslim universities and communities in New Delhi, and now include a broad section of the Indian public nationwide.

A British colonial-era law banning the assembly of more than four people was in place in parts of the Indian capital as well as in several cities in Assam and Uttar Pradesh, where a motorised rickshaw driver was fatally shot during a protest in Lucknow.

Authorities erected roadblocks and turned areas around mosques in New Delhi, Lucknow and other Muslim-dominated areas into security fortresses to prevent widespread demonstrations after Friday prayers.

They waved Indian flags and shouting slogans against the government and the citizenship law – which critics contend marginalises Muslims and threatens India's secular democracy in favour of a Hindu state. (Sipa USA)

Police temporarily held 1200 protesters in New Delhi on Thursday and hundreds of others were detained in other cities after they defied bans on assembly. Most protesters were released later in the day.

While some see the citizenship law as a slight against Muslims, others, including some Hindu conservatives in Modi's Bharatiya Janata Party, fear it will encourage immigration to India, where public services for its 1.3 billion people are already highly strained.

"In effect, some of the BJP's own rank and file, the very people the party has sought to help, have come out against the law," said Michael Kugelman, deputy director of the Asia Program at the US-based Wilson Center.

Mr Kugelman said that the government's failure to respond to the protests, except to accuse political opponents of orchestrating them, is "likely to galvanise the protesters even more".

The protests come amid an ongoing crackdown in Muslim-majority Kashmir, the restive Himalayan region stripped of its semi-autonomous status and demoted from a state into a federal territory last summer.

They also follow a contentious process in Assam meant to weed out foreigners living in the country illegally.

Nearly two million people were excluded from an official list of citizens, about half Hindu and half Muslim, and have been asked to prove their citizenship or else be considered foreign.

India is also building a detention centre for some of the tens of thousands of people the courts are expected to ultimately determine have entered illegally. Modi's interior minister, Amit Shah, has pledged to roll out the process nationwide.