This is the heart-breaking moment a devastated parent in Hong Kong kneels on the ground in tears as she begs riot police to spare her child's life during a siege to arrest protesters in a university.

Police using tear gas and batons today fought running battles with young activists who tried to break through a security cordon that trapped hundreds of them at the city's Polytechnic University.

The woman, whose child is believed to be inside the war-zone-like institute, can be seen crying uncontrollably as she yells 'release my child, release my child' outside the campus, according to footage released by local media.

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Footage from RTHK News shows a woman in Hong Kong yelling 'release my child, release my child' while kneeling on the ground outside the Polytechnic University. Police have stormed the campus, firing rubber bullets and tear gas to pin back protesters armed with petrol bombs

A police officer pins down a protester trying to flee from the Hong Kong Polytechnic University in Hong Kong today. A security cordon has left hundreds of activists trapped on campus

A student tries to extinguish a fire at the entrance of Hong Kong Polytechnic University today

The woman made the desperate plea for help after two students surrendered to police after walking out of a footage bridge leading to the Polytechnic University, reported Radio and Television Hong Kong.

The station quoted another mother who said her son was still trapped in the university.

The mother said she had come to wait for her son.

She said she had been informed that he son had not been injured, but she felt heart-broken to hear her son's 'desperate' voice on the phone.

She criticised the government for labelling those who chose to remain on campus 'rioters', adding the government should not blame young people for all problems in society.

Masked protesters hold British and American flags as well as a sign reading 'Save Us' as they stand near Hong Kong Polytechnic University today. For days, protesters fortified the campus to keep police from getting in. Cornered by authorities, they were trying to get out today

Riot police arrest a protester during clashes outside the Hong Kong Polytechnic University

Protesters set a fire as they march to Hong Kong Polytechnic University in Hong Kong today

Hong Kong police laid siege to the Polytechnic University today, firing rubber bullets and tear gas to pin back protesters armed with petrol bombs and other weapons and stop them from fleeing amid fears of a bloody crackdown.

The raid came as the city's High Court ruled an emergency law which banned protesters from wearing face masks 'unconstitutional'.

Police said they would stop enforcing the ban immediately.

Social media footage shared by Hong Kong Free Press purports to show hundreds of people forming massive human chains near the university's campus to pass supplies to the activists who attempt to break through the police cordon.

Another clip purports to show protesters building barricades on Nathan Road in a matter of minutes in a bid to stop riot police.

A picture taken near the university earlier today shows two masked protesters holding a placard reading 'save us' as well as the British and American flags as they begged the Western countries to help them.

For days, protesters fortified the campus to keep police from getting in. Cornered by authorities, they were trying to get out.

A protester crosses a road full of bricks in the Jordan district of Hong Kong as the city is witnessing its most tense days yet since mass demonstrations broke out five months ago

A riot police officer fires tear gas at protesters during clashes outside the Hong Kong Polytechnic University. China has urged the West to stop interfering in its internal affairs

Police used water cannons, tear gas and rubber bullets, while protesters used Molotov cocktails, arrows and bricks

It wasn't clear if any of those inside escaped.

Police had stormed the campus overnight and made dozens of arrests before retreating. They are intent on talking all the protesters into detention.

The European Commission said today that violence in response to the escalating anti-government protests in Hong Kong was unacceptable and called on law enforcement authorities to keep their action 'strictly proportionate'.

Britain said it was seriously concerned by the violence on both sides at Hong Kong universities and called for safe passage and medical assistance be given to those trapped at the campuses.

China's ambassador to London urged foreign countries, including the United States and Britain, to stop interfering in Hong Kong's internal affairs.