The Ministry of External Affairs (MEA) late on Sunday summoned the senior-most UK diplomat in India to convey its strong protest after some pro-Khalistani groups allegedly took down the Tricolour at the Indian High Commission in London.
MEA spokesperson Arindam Bagchi tweeted: "India lodges strong protest with UK", along with a ministry statement.
Some pro-Khalistani groups staged a demonstration at the Indian High Commission in London over Punjab government's crackdown against self-styled radical preacher Amritpal Singh.
The MEA, in a statement, said an explanation was demanded for the complete absence of the British security that allowed these elements to enter the High Commission premises.
"She was reminded in this regard of the basic obligations of the UK government under the Vienna Convention," it said.
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A statement said it finds unacceptable the indifference of the UK government to the security of Indian diplomatic premises and personnel in the UK.
"It is expected that the UK government would take immediate steps to identify, arrest and prosecute each one of those involved in today's incident, and put in place stringent measures to prevent the recurrence of such incidents," it added.