Hong Kong (dpa) - Hong Kong's upcoming district council elections on November 24 are looking less likely after a week of unrest and violence - particularly on university campuses - rages across the city, the government said.

The comments came amid a stand-off between activists and police officers at Hong Kong's Polytechnic University, the latest hotbed for fierce clashes between authorities and anti-government protesters.

Several candidates were assaulted in the run-up to Sunday's elections, including pro-democracy candidates and a controversial pro-establishment legislator named Junius Ho, whom critics allege is linked to organized crime groups.

Patrick Yip, the secretary for constitutional and mainland affairs, warned that anti-government protests on the weekend had reduced the chances of the elections going ahead as scheduled.

"I must say that postponing the elections is a difficult decision to make and we will not take this step unless absolutely necessary," Yip told local public broadcaster RTHK.

In order for the elections to take place, violence, roadblocks and the destruction of public transport facilities must end, Yip said. The government has said it is rolling "full steam" ahead with election preparations but said stopping violence is its number one priority.

Prior to the announcement, surveys showed an increase in support for pro-democracy candidates.

On Monday, the Hong Kong Polytechnic University was surrounded by riot police and cordoned off. The night before, police issued an ultimatum for protesters inside to leave before 10 pm (1400 GMT) through a designated exit. Shortly after, tear gas was fired by police and a barricade drawn up by protesters at the designated exit spot, leading to further clashes and an escalation of violence.

As many as 200 protesters remain trapped inside the campus with no viable exit route. Those who attempted to leave were immediately arrested, with the exception of the press. In the afternoon, more than 100 protesters ran out of the campus in an attempt to escape, but they were driven back into campus by a barrage of teargas.

Liu Xiaoming, China's ambassador to London, told reporters that the violence in Hong Kong had left the city in an "extremely dangerous situation."

Liu said the protests had "nothing to do with so-called democracy or freedom" but represent an attempt by "a few violent offenders ... to destabilize Hong Kong."

He warned that Hong Kong faces an "unimaginably dreadful" future if the protests continue, Liu said.

University campuses have been the site of intense fiery clashes between protesters and police in the past week, with the Polytechnic University being the last remaining stronghold not yet abandoned.

Protesters barricaded campuses and armed themselves with molotovs, petrol bombs and even bows and arrows. They also blocked key transportation routes in an effort to persuade Hong Kong residents to go on strike against the government.

The Hong Kong High Court ruled earlier on Monday that a controversial mask ban, enacted just over a month ago by Chief Executive Carrie Lam, was unconstitutional. The controversial law, enacted by the government in a bid to quell protests, ultimately drove more protesters out onto the streets.

The court ruled that the mask ban imposed restrictions on people's fundamental rights. More than 24 pro-democracy legislators had asked for a judicial review of the mask law.

Hong Kong's protests began in June to demand the suspension of now-suspended legislation that would have allowed extraditions to mainland China. The movement has since evolved into calls for greater democratic reforms and an independent investigation into police violence.