Up to 200 Hong Kong and Chinese students clashed in the city on Wednesday after a pro-democracy rally was hijacked by counter-demonstrators.
Bottles were thrown and police scrambled as trouble flared outside the historic Town Hall.
One passer-by reported having her crutch stolen, which was then waved as a threatening weapon.
Another demonstration has been planned for Saturday in the city – home to an estimated 7,000 Chinese and Hong Kong citizens – leading to fears of more clashes.
Speaking to The Independent, Ben Miskell, a local councillor and eyewitness to Wednesday’s clashes, said: “These were outrageous scenes for a British city.
“The Chinese students descended on mass to intimidate what was a peaceful protest.
“It was ugly, and there was a real sense it could have grown out of control if the police hadn’t arrived.
“In Britain you have a right to peaceful protest, and that must be protected from thuggery and intimidation.”
The trouble started as 30 students from Hong Kong ran a stall explaining the current situation in their homeland, where many had spent the summer.
Apparently antagonised, an estimated 150 Chinese – many carrying the national flag and playing the country’s anthem on their phones – carried out an impromptu counter demonstration said to have been organised via Chinese messaging app WeChat.
“There were bottles thrown and chants about Hong Kong students being insects,” said Mr Miskell.
“In the end, the smaller group had to be escorted into the Town Hall for their own safety, and were then given a police escort out.”
Several of the students had told him they were facing intimidation on campus because of events in Asia, he added.
South Yorkshire Police confirmed officers attended the scene “to provide reassurance and assist the groups when leaving”, but said no arrests had been made.
A spokesperson said: “We have had one report from someone saying a bottle had been smashed, however no reports of injuries.”
A University of Sheffield spokesperson said: “We support the rights of students to share, debate and raise awareness of issues that are important to them.
“However, we prioritise the wellbeing and safety of all our students and we ask students to peacefully respect each others’ views.”
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