Bob Chan, who is originally from Hong Kong, says he was with a group demonstrating against Chinese President Xi Jinping outside the consulate in Manchester, northern England, when masked men pulled him inside and kicked and punched him.

Consul-General Zheng Xiyuan said his staff, including himself, had been defending themselves after protesters had stormed the grounds in an unprovoked attack.

Greater Manchester Police said they had been gathering evidence from mobile phone footage and witnesses to establish the full circumstances of what had happened.

There have been no arrests so far, but they had "identified a number of offences including assaults and public order offences".

"We’re continuing to gain a clearer understanding of the timeline of events that led to an initially peaceful protest escalating in the way it did, and this has seen us identify a number of offences and potential suspects and victims," Assistant Chief Constable Chris Sykes said.

Chan, aged in his 30s, said he suffered bruising to his eye, head, neck and all over his back.

The incident sparked another diplomatic spat between Britain and China, whose relationship has soured in recent years.

Last week, Britain's domestic spy chief said any intimidation and harassment of British nationals or those living in Britain would not be tolerated.