The Indian High Commission in the United Kingdom issued a statement after New Delhi's High Commissioner to the country, Vikram Doraiswami, was blocked from entering a gurdwara in the city of Glasgow by pro-Khalistan extremists.
It said three protesters - whom it described as "non-local extremist elements" - threatened its diplomats and one tried to open the door of Doraiswami's car, prompting the officials to abandon the visit.
A spokesperson for Scotland's police force said officers had been called to a report of a disturbance near the gurdwara, but there were no injuries. Enquiries were ongoing and no arrests had been made, police added.
"Glasgow Gurdwara strongly condemns such disorderly behaviour to disrupt the peaceful proceedings of a Sikh place of worship," the religious body said in a statement to media.
A British government minister expressed concern that the visit by senior Indian diplomat to a Sikh temple in Glasgow had been disrupted by protesters.
"The safety and security of foreign diplomats is of utmost importance and our places of worship in the UK must be open to all," junior foreign office minister Anne-Marie Trevelyan said in a post on social media.
Long-standing tensions between some Sikhs and the Indian government have increased since Canada earlier this month linked the killing of a Sikh separatist advocate near Vancouver to Indian government agents - allegations which India has dismissed as "absurd".