A suspected Hindu nationalist Thursday live-streamed himself minutes before opening fire on university students protesting against India's new citizenship law.

One student was reportedly shot in the hand before police arrested the alleged gunman, who timed his attack to coincide with the anniversary of the assassination of independence hero Mahatma Gandhi in 1948 by a Hindu radical. Video circulating on social media showed the man brandishing a handgun and confronting protesters while shouting "Yeh lo azadi" ("Here is your freedom") and "Long live Delhi police".

In the background, dozens of police can be seen watching proceedings. The highly charged word "azadi" was previously associated with Kashmiri separatists, but has been used widely in the past more than a month of protests against the citizenship law.

The law makes it easier for persecuted religious minorities from three neighbouring countries to get Indian citizenship, but not if they are Muslim. Critics say this forms part of Prime Minister Narendra Modi's master plan to remould India as a purely Hindu nation, marginalising its 200 million Muslims, something Modi denies.

Before Thursday's incident, the alleged gunman went live on Facebook as he walked around the protest area. "On my last journey, take me draped in saffron and shout slogans of Hail Lord Ram," one post on his page read -- a popular chant for Hindu nationalists. Saffron is a colour associated with Hinduism -- and with Modi's Hindu nationalist Bharatiya Janata Party  -- while Ram is an important deity.

"Shaheen Bagh, Game Over," read another, referring to massive protests against the citizenship law taken up by women and children in the Indian capital.

Afterward the shooting several thousand people gathered at the site, an AFP reporter said. Some pushed against barriers, and police responded with water cannon, media reports said.