A man has been arrested on suspicion of violent disorder after a crowd gathered and windows were broken at the Indian High Commission in London.
Police were called to the building in Aldwych, Westminster, on Sunday.
Videos on social media showed a crowd waving yellow "Khalistan" banners and a man detach the Indian flag from the first-floor balcony of the building.
The Metropolitan Police said two security guards were injured and an investigation has been launched.
PA news agency said crowd members were believed to be supporters of a Sikh separatist movement.
Officers were called to the Indian High Commission at about 13:50 GMT on Sunday.
Upon arrival "the majority of those present had dispersed prior to the arrival of police", said the Met.
The force's spokesperson said "windows were broken" and two members of security staff sustained minor injuries which did not require hospital treatment.
The Met said inquiries were continuing.
Responding to the incident, London's mayor Sadiq Khan said he condemned "the violent disorder and vandalism that took place".
"There is no place in our city for this kind of behaviour", he tweeted.
The British High Commissioner to India Alex Ellis described the incident as "disgraceful" and "totally unacceptable".
Foreign Office minister Lord Tariq Ahmad of Wimbledon said he was "appalled" and the government would take the security of the Indian High Commission "seriously".
"This is a completely unacceptable action against the integrity of the Mission and its staff", he said.
