Conservative MP Jacob Rees-Mogg was caught up in a scuffle after protesters disrupted a speech he was giving at a student event.
Videos online show the backbencher surrounded by a group of people, with shouting audible in the background.
BBC reporter James Craig, who was at the University of the West of England (UWE) event, said security cleared the protesters within five minutes.
Mr Rees-Mogg, who resumed his speech, said they were “entitled to protest”.
However, he said it was “sad” they would not engage and discuss views to which they objected.
Mr Rees-Mogg had been speaking at an event organised by the university’s Politics and International Relations Society.
Police said they had launched an investigation into the scenes at the Frenchay Campus in Bristol, but no arrests had yet been made.
The university said on Twitter it was “absolutely appalled by the conduct of a small number of attendees” at the event.
The statement continued: “It is our understanding at this stage that a small group of protesters broke into the lecture theatre where the event was due to take place via the back doors.
“We understand that these protesters were not UWE Bristol students and did not have tickets for the event.
“We support the democratic right to free speech and peaceful protest. However, we strongly condemn the actions of protesters who disrupted normal debate and behaved in this way.
“There is no place for such action on a university campus or in a civilised society.”
At the scene: James Craig, BBC Somerset
It was due to be a fairly routine event – Jacob Rees-Mogg was booked to speak to a few hundred students at a ticketed event.
He would’ve spoken for about half an hour before taking questions.
Just a few minutes after he started speaking, a group of protestors came into the back of the lecture theatre and started shouting anti-Conservative rhetoric, very loudly, trying to shout him down.
Rather than halting the event, or ignoring them, Mr Rees-Mogg walked up to the back of the theatre to try and talk them down.
At that point, various other members of the audience got involved, leading to the scuffle which happened.
It looked to me that Mr Rees-Mogg was actually pushed and shoved, although he insists he wasn’t.
But it was a very aggressive and unexpected scene.
After the scuffle, Mr Rees-Mogg said: “Some people who don’t agree with me wanted to make their point, and I don’t object to this.
“I think we live in a free society and freedom of speech is very important.
“And people like me, who advocate freedom of speech, support it when it’s not exactly what we want, as well as when it is what we want.”
Universities Minister Sam Gyimah branded the protesters’ behaviour “thuggish”, adding: “Free speech under the law is fundamental to our democracy.”
He praised Mr Rees-Mogg for “not being cowed into silence”.
Shadow education secretary Angela Rayner condemned the behaviour of “those who tried to attack” the MP, branding their actions “extremely intimidating”.
Liberal Democrat Deputy Leader Jo Swinson said it was “deeply worrying to see violent tactics by political opponents”.
A post on the society’s Facebook page, advertising the event, said it would be a “chance to talk to an experienced parliamentarian about the issues of the day, what it’s like to be an MP and how you can get there”.
On Twitter, eyewitness Chloe Kaye, who filmed the scuffle, described “a huge amount” of physical violence.
Others condemned the protesters.
Avon and Somerset Police said officers were called at about 18:30 GMT following a report of a public order incident.
“An investigation is under way to see if any criminal offences were committed,” the force said, while appealing for mobile phone footage to be passed on to them.