UC Berkeley has cancelled a planned speech by far-right commentator Milo Yiannopoulos after violent protests erupted on campus.

Officials were forced to call off the event when a crowd of up to 1,500 people reportedly started toppling street lamps, setting fires and shot fireworks at the venue.

The Breitbart editor and “alt-right” Twitter troll had been invited by the Berkeley College Republicans to address an audience of 500.

The Martin Luther King Jr student union had already been heavily reinforced behind several layers of police barricades however violence escalated and the police placed the campus on lockdown, advising students to shelter in place or leave the area.

“It was simply impossible to maintain order given the level of threat, disruption, and violence,” the administration said in a statement.

Dozens of extra police officers had been placed on duty and attempted various methods of crowd control, however they were unable to calm the demonstrations.

“I have been evacuated from the UC Berkeley campus after violent left-wing protesters tore down barricades, lit fires, threw rocks and Roman candles at the windows and breached the ground floor of the building,” Mr Yiannopoulos said in a statement posted on Facebook.

“My team and I are safe. But the event has been cancelled. I'll let you know more when the facts become clear. One thing we do know for sure: the Left is absolutely terrified of free speech and will do literally anything to shut it down.”

More than 100 faculty members signed a letter urging the university to cancel the speech.

However, Berkeley’s chancellor said it would be “unconstitutional” to shut down a debate “based on the viewpoints those speakers may express.”

The conservative figure was due to deliver the speech as part of his controversial anti-political correctness tour “Dangerous F****t.”

A man was shot and wounded at protests outside his talk at the University of Washington on 21 January and protests at UC Davis earlier in the month prompted campus Republicans to cancel his appearance.