The University of British Columbia says 32 of its students on exchange in Hong Kong have either left the city or confirmed they are safe after the school urged them to leave the area for their own well-being.

Hong Kong has been roiled by six months of anti-government protests. The once peaceful demonstrations have steadily intensified, and are now punctuated by shootings and violent clashes between protesters and police.

UBC administration said Friday that staff had reached out to exchange students advising them to leave their schools. An email from university officials Monday confirmed 11 students have left Hong Kong, while the remaining 21 "are safe and accounted for."

The email said the school is helping students with travel plans. Any student who is choosing to stay in Hong Kong has been asked to watch for directives from their host university and monitor International SOS for updates and guidance on how to stay safe.

Anti-government demonstrators block a road near the Hong Kong Polytechnic University on Nov. 18. (Adnan Abidi/REUTERS)

Simon Fraser University says it has 17 students on exchange there and they have all confirmed they are safe. The university says it is working with each student on their return to Canada.

Montreal's McGill University, Queen's University in Kingston, Ont., and the University of Toronto are also urging all their students to head home.

Universities have become the latest battleground for protesters, who used gasoline bombs and bows and arrows in their fight to keep riot police off of two campuses in the past week.

Police backed by armoured cars and water cannon tightened their siege of Hong Kong Polytechnic University (PolyU) Monday, where hundreds of protesters remained trapped in a sign of a fresh escalation for the movement.

Colin Robertson, a former Canadian diplomat and a former Canadian consul in Hong Kong, expressed sympathy for the students locked inside who are protesting for freedoms many in Canada take for granted.

He says the protests have taken a worrying turn.

"When you look at the pictures today, and you know this has gone on for six months, it's hard to be optimistic about what might happen," he said. "I hope I'm wrong."

Protests raged across other parts of the city, fuelled by public anger over the police blockade of the school and the desire to help the students stuck inside.

The UBC students had been studying at four different schools — Chinese University of Hong Kong, City University of Hong Kong, Hong Kong University of Science and Technology, and Hong Kong University — and not the polytechnic university, the Canadian school said.

The protests started peacefully in early June, sparked by proposed legislation that would have allowed criminal suspects to be extradited to the mainland. By the time the bill was withdrawn, the protests had hardened and broadened into a resistance movement against the territory's government and Beijing.

Jane Li, a born-and-raised Hong Konger who now lives in Vancouver, is a spokesperson for the group Vancouver Hong Kong Political Activists.

Li says the protest movement has reached a tipping point.

"This morning I got on the phone with a friend and she said, 'I don't know if there's going to be a tomorrow.' That really hit me," Li said.

"It seems like for both sides, it's going to be a really violent ending."

Activists see the extradition bill as an example of Hong Kong's eroding autonomy under Beijing rule since the handover from colonial power Britain in 1997.