A firebrand fugitive Sikh separatist has posted a video taunting Indian authorities after a fruitless almost two-week manhunt involving thousands of police and internet shutdowns.

Amritpal Singh has risen to fame in recent months demanding the creation of Khalistan, a separate Sikh homeland, the struggle for which sparked deadly violence in the 1980s and 1990s.

Punjab police have been hunting Singh since March 18, cutting off mobile internet in the Sikh-majority northern state of 30 million people for days, arresting more than 100 of his followers and banning gatherings of more than four people in places.

After reported sightings in Delhi, in the video posted on social media on Wednesday, Singh called the police operation an "attack on the Sikh community".

"I was neither afraid of arrest earlier, nor am I now. I am in high spirits. Nobody could harm me. It is the grace of God," he said.

There has been no independent verification of the video but there were few doubts that it is genuine.

The manhunt has sparked protests by Sikhs outside Indian consulates in Britain, Canada and the United States, with demonstrators smashing windows in San Francisco and reportedly vandalising a Gandhi statue in Ontario.

India has summoned top US, British and Canadian diplomats in New Delhi to complain and press for improved security at Indian missions in their countries.

Singh's video was posted on Twitter accounts based in Britain and Canada, which the social media company took down in India following government requests, reports said.

Twitter has also blocked for Indian users the accounts of several prominent Sikh Canadians who criticised the crackdown, including MP Jagmeet Singh, as well as several journalists, according to the reports.

Punjab -- which is about 58 percent Sikh and 39 percent Hindu -- was rocked by a violent separatist movement for Khalistan in the 1980s and early 1990s in which thousands of people died.

India has often complained to foreign governments about the activities of Sikh hardliners among the Indian diaspora who, it says, are trying to revive the insurgency with a massive financial push.