Indian police arrested on Tuesday the leader of a vigilante group devoted to protecting cows who had been accused of inciting deadly religious riots near New Delhi in July.

Monu Manesar leads a chapter of the radical Hindu right-wing group Bajrang Dal and is a suspect in the mob lynching in February of two Muslim men accused of cow smuggling.

Cows are considered sacred by Hindus and their slaughter is illegal in many Indian states.

Manesar remained free and continued to post inflammatory anti-Muslim content regularly on Facebook and Instagram for months after authorities linked him to the murders.

He announced in July plans to attend a Hindu procession in Nuh, a largely Muslim district near the capital.

At least six people were killed and dozens more injured in the resulting unrest, which continued for days and spilled over to Delhi's outskirts.

Nuh district police officer Shubhjeet Singh confirmed Manesar's arrest on charges of spreading hateful content on social media.

Singh said Manesar would be handed over to police in Rajasthan state, where charges have been registered against him over the February double-murder.

Manesar ultimately did not attend the July procession in Nuh, which saw cars set alight and stones hurled at participants.

The violence soon spread to nearby Gurugram, a key business centre and satellite of Delhi where Nokia, Samsung and other multinationals have their Indian headquarters.

In one neighbourhood, a mob of around 200 people armed with sticks and stones looted several Muslim-owned meat shops and set fire to a restaurant while chanting Hindu religious slogans.

Manesar regularly posted videos celebrating attacks on Muslims accused of transporting or killing cows.

India has seen numerous outbreaks of sectarian violence between majority Hindus and its 200-million-strong Muslim minority since Hindu nationalist Prime Minister Narendra Modi took office in 2014.

Critics have accused his government of turning a blind eye to vigilante campaigns against Muslims in the name of cow protection and the lynching of men accused of involvement in cattle slaughter.