A student was shot after a man opened fire during a protest against a controversial citizenship law in New Delhi on Thursday, police said.

The gunman was overpowered and detained soon after the incident outside the city's Jamia Millia Islamia university, senior police officer Chinmay Biswal said.

The protestors were marching from the university to the mausoleum of India's independence leader Mahatma Gandhi on his death anniversary.

A student identified as Shadaab Farukh was shot in the hand and was taken to a nearby hospital for treatment.

India has witnessed protests over the past weeks against the new law that critics claim goes against India's secular constitution.

It omits Muslims from religious groups from three neighbouring countries who are entitled to fast-track citizenship.

Police sources told broadcaster NDTV that the gunman was identified as a 19-year-old who had gone live on Facebook minutes after he drew out his gun.

Later on Thursday evening, over a thousand students continued their protests in the area and police had requested reinforcements.

Protests over the citizenship law began at the Muslim Jamia Millia Islamia university last month that saw violence including buses and vehicles being burnt. Police had stormed the campus and faced allegations of assaulting students.

India's Hindu nationalist Bharatiya Janata Party government says the law would not affect the rights of any citizen of India, Hindu or Muslim, and has accused opponents of spreading misinformation.

A number of petitions challenging the validity of the new law are being heard by the Supreme Court.