Britain should take action after a violent incident during protests outside India’s embassy in London last month, India’s Prime Minister Narendra Modi told British counterpart Rishi Sunak on Thursday.

New Delhi has been upset about protests and vandalism by Sikh separatists - who seek an independent Sikh homeland called Khalistan - outside the Indian High Commission in London and elsewhere in the US and Canada.

In a telephone conversation with Sunak, Modi called for “strong action against anti-India elements” by the British government following the incident, Modi’s office said in a statement.

Sunak condemned the incident as “unacceptable violence”, his Downing Street office said in a readout of the call.

“He stressed that extremism had no place in the UK and updated on the steps being taken to ensure the security of Indian High Commission staff,” Sunak’s office added.

UK-India bilateral ties became tense last month when protesters in London with Khalistan banners reportedly removed an Indian flag from the balcony of the High Commission during a protest in which the building's windows were also broken.

British foreign minister James Cleverly had condemned the violence last month but Thursday’s call was the first official discussion between Modi and Sunak about the incident.

Both sides also said Modi and Sunak agreed on needing to speed up negotiations for a free trade agreement between Britain and India, which a British newspaper report said this week had stalled over the incident.

The two leaders are also due to meet at the G7 summit in Japan next month and the G20 in India later this year.

The demonstration outside the Indian High Commission was staged to denounce recent police action in the Sikh-majority Indian state of Punjab against a pro-Khalistan Sikh preacher.

The demand for Khalistan, which led to violence that killed tens of thousands of people in the 1980s and 1990s, has revived in sections of the Sikh population in India and overseas.

Indian officials conveyed concerns over pro-Khalistan groups to British counterparts during a meeting of interior ministry officials from both countries in New Delhi on Wednesday.

In the meeting, the Indian side requested better cooperation with Britain to tackle “the misuse of UK’s asylum status by the Pro-Khalistani elements to aid and abet terrorist activities in India and with UK,” the Indian government said.