A man protesting outside the Chinese consulate in the northern British city of Manchester was dragged onto the consular grounds and beaten.

The scuffle at the consular gates in Manchester on Sunday took place as protesters from Hong Kong demonstrated against China’s leader, Xi Jinping, who is expected to win a third term leading the country during this week’s Communist Party Congress in Beijing. Banners and posters placed outside the consulate’s entrance called for an end to the Communist Party and depicted Xi wearing only a crown and underwear.

Video footage that circulated widely online showed a group of men, presumably from the consulate, ripping up posters and dragging one protester through the consulate’s gate, where they wrestled him to the ground and beat him.

During the scuffle, Manchester police officers stepped onto the consular property to separate the protester from his attackers. The force said on Monday it was investigating the incident and had established an online portal for people to submit additional information about the incident.

“It is clear what began as a peaceful protest unexpectedly escalated and our officers acted professionally in response to a hostile and dynamic situation to help the victim,” the Manchester police wrote in a statement on Monday. It added that the man who was attacked had sustained “several physical injuries” and had been treated at a hospital overnight.

A spokesman for the Chinese consulate was quoted by the BBC criticising protesters for hanging an “insulting portrait” of Xi at the building’s main entrance. “This would be intolerable and unacceptable for any diplomatic and consular missions of any country,” the spokesman said, according to the BBC. “Therefore, we condemn this deplorable act with strong indignation and firm opposition.”