A legal row has broken out after a teenage girl was arrested outside the UK’s Consulate General in central Hong Kong, in what activists claim was a breach of British diplomatic territory.

The arrest took place on Saturday when riot officers searched demonstrators on a paved area in front of the Consulate where people have camped out in a peaceful human rights protest for close to 60 days. Reports suggest that the teenager was found to have a can of spray paint.

In a statement, the police said that they “responded to an incident at Supreme Court Road reported by a consular staff. Upon police arrival and investigation, one female (aged 15) was arrested outside a consulate in Admiralty for the offence of ‘Criminal Damage’.”

However, human rights groups allege that officers were potentially in breach of diplomatic norms, using site plans to back their claims that the pavement was technically British territory.

“I urge the British government to issue an urgent statement both in defence of the right to peaceful protest and its own boundaries and diplomatic protocols,” said Benedict Rogers, chairman of Hong Kong Watch, urging diplomats to monitor the girl’s case.