Students from the the University of Sheffield supporting pro-democracy protests in Hong Kong have clashed with others backing the Chinese government.
The pro-Hong Kong group said they faced intimidation and had a bottle thrown at them.
Police confirmed they were called to Fargate in Sheffield city centre amid reports of fighting.
Students had to be escorted to the Town Hall and took refuge in the debating chamber, according to a councillor.
A group of about 30 people had gathered to "raise awareness" of the anti-government protests which have rocked Hong Kong for months.
According to the group a counter-protest was arranged by other students over the Chinese messaging app WeChat.
They are said to have referred to the pro-democracy group as "insects" while singing the Chinese national anthem.
The students said at one point a crutch was stolen from a woman passing by which they believed was going to be used as a weapon, the Local Democracy Reporting Service said.
They also said a beer bottle was launched at the group and a flag was stolen and broken.
Labour councillor Ben Miskell said he left a full council meeting after getting a message from the pro-democracy protesters saying they were under attack.
He said: "These aren't hardened protesters, they just want to protect their way of life and their families' way of life in Hong Kong."
One student, who did not want to be named, told the BBC: "We are quite afraid of what is happening here and whether we're going to be safe in class.
"There's lots of Chinese people on campus and I'm worried what will happen if I'm alone."
A guide to the Hong Kong protests
South Yorkshire Police confirmed PCSOs were in attendance and said several other officers were called to the scene "to provide reassurance and assist the groups when leaving".
"From CCTV monitoring and PCSOs at the scene, it doesn't look as though a fight actually broke out," the force said.
"We have had one report from someone saying a bottle had been smashed, however no reports of injuries."
A University of Sheffield spokesperson: "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 other's views."