• Video report by ITV News Senior International Correspondent John Irvine

Police in Hong Kong have tightened their siege of a university campus where hundreds of protesters remained trapped in the latest dramatic clashes.

The pitched battle for control of the campus of Hong Kong Polytechnic University has been the focus of the latest protests as demonstrators for days fortified the campus to keep the police out.

It comes as the Chinese ambassador to the UK has warned the Government against interference in Hong Kong's affairs.

Liu Xiaoming has accused the Government and the Foreign Affairs Committee of publishing reports "making irresponsible remarks" on Hong Kong.

Mr Xiaoming added some UK politicians had planned to present an award to a "chief propagandist of Hong Kong independence" who has "instigated extreme violence".

Liu Xiaoming has been speaking in London. Credit: PA

Speaking in London, Mr Xiaoming said: "The British Government and the Foreign Office committee of the House of Commons published China-related reports making irresponsible remarks on Hong Kong.

"What is worse, certain British politicians even planned to present (an) award to a chief propagandist of Hong Kong independence and who has instigated extreme violence."

Hong Kong itself has witnessed a tense standoff between police and around 200 protesters who have barricaded themselves inside a university campus for several days.

Protesters began attempting to escape from Hong Kong Polytechnic University's campus, on Monday, but were met with tear gas and baton-wielding police, and some were arrested.

Demonstrators responded by hurling petrol bombs at armoured vehicles, setting a truck alight.

Police have warned that all the protesters on the campus could be charged with rioting, which carries a penalty of up to 10 years in prison.

Meanwhile, Hong Kong's high court issued a ruling on Monday which said that the face mask ban infringes on fundamental right.

The government used its emergency powers to impose the ban last month.

The court said it did not consider anti-mask laws unconstitutional in general, but in this case, the law infringed on fundamental rights further than was reasonably necessary.

Elsewhere, the city's working week started with multiple protests that disrupted traffic and many schools did not open.

A policeman in riot gear points his weapon as protesters try to flee from the Hong Kong Polytechnic University Credit: Ng Han Guan/AP

The protests started peacefully in early June, sparked by proposed legislation that would have allowed criminal suspects to be extradited to mainland China.

But by the time the bill was withdrawn, the protests had hardened and broadened into a resistance movement against the territory’s government and Beijing.

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

Earlier on Monday, a lull had settled on the campus as the president of the university said in a video message that that police have agreed to suspend their use of force.

Jin-Guang Teng said police would allow protesters to leave and he would accompany them to the police station to ensure their cases would be processed fairly.

“I hope that you will accept the proposed temporary suspension of force and leave the campus in a peaceful manner,” he said.

However, it seemed unlikely the protesters would accept the offer given that they would all likely be arrested.