As the pro-democracy protests continue in Hong Kong, a video has emerged of a police officer pepper spraying a man directly in the face.

The footage, which has been widely shared on social media, is being held up as an example of authorities’ harsh crackdown on demonstrations.

Thousands of people occupying the streets near Government headquarters in the city’s Admiralty district were hit with volleys of tear gas and pepper spray over the weekend as riot police tried to beat protesters back with baton charges.

In the footage taken on Sunday, protesters are seen attempting to shield themselves with umbrellas as police behind a barricade wrench them them out of their hands to douse them with pepper spray.

As the group retreats, a middle-aged man stops to wipe the searing liquid from his eyes and talks to the crowd.

When an apparently unprovoked police officer taps him on the shoulder, he turns round only to be hit directly in the face with pepper spray, to shouts from watching protesters.

By Wednesday afternoon, the footage taken by Hong Kong’s Digital Broadcasting Corporation had been shared more than 10,000 times on Facebook.

The demonstrators were left largely alone on Monday and Tuesday after an international outcry but student leaders have warned that if their demands are not met, action will escalate.

Protest numbers swelled today, a national holiday, to tens of thousands, including many families with children, couples, students, retirees and foreigners who live in the city. The Occupy Central movement started following the Chinese Government’s refusal to let them select their own candidates for leadership elections in 2017, allowing only pre-approved politicians to stand.

One of the key demands of the occupation is the immediate resignation of the city’s unpopular Beijing-backed Chief Executive Leung Chun-ying, along with proper consultation on political reform to allow free and fair elections.

If he does not resign by Thursday, student leaders have threatened to occupy key Government buildings, risking a harsh police response.

Lester Shum, vice secretary of the Hong Kong Federation of Students, said protesters would not interfere with essential Government services like hospitals and social welfare.

In pictures: Hong Kong democracy protest 2014 Show all 32 1 /32 In pictures: Hong Kong democracy protest 2014 In pictures: Hong Kong democracy protest 2014 Hong Kong protests Pro-democracy protesters make gestures to the police outside Central Government Complex, 1 December EPA In pictures: Hong Kong democracy protest 2014 Hong Kong protests Pro-democracy protesters build barricades at the bottom of an escalator outside Central Government Complex, 1 December Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Police and protesters scuffle near the office of the Chief Executive in Hong Kong as clashes erupt again on 1 December Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests An injured protester lies prostrate on the ground as chaos surges around her on 1 December AP In pictures: Hong Kong democracy protest 2014 Hong Kong protests Thousands of protesters gathered in Hong Kong's Victoria Square to commemorate the anniversary of Tiananmen Square in June Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests A protester raises his umbrellas in front of tear gas fired by riot police in the main street to Hong Kong's financial Central district in September REUTERS In pictures: Hong Kong democracy protest 2014 Hong Kong protests Police officers stand guard during clashes with pro-democracy protesters in Hong Kong on September 28, 2014 AFP/Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Police officers stand in a cloud of tear gas during a demonstration in Hong Kong on September 28, 2014 AFP/Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests A demonstrator gestures opposite policemen during a pro-democracy protest in Hong Kong on 28 September 2014 AFP/Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests A man's face is doused with water after police fired tear gas at protesters on 28 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Riot police stand guard outside of the Hong Kong Government Building on 28 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests A protester walks in tear gas fired by riot policemen on 28 September 2014 Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests Protesters hold umbrellas against a line of police officers near the government headquarters in Hong Kong on 28 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests A protester raises his umbrellas in front of tear gas fired by riot police on 28 September 2014 Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests housands of demonstrators storm onto a highway after breaking through police cordons during ongoing pro-democracy protests in Hong Kong on 28 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Protesters disperse as riot police fire teargas outside the government headquarters in Hong Kong on 28 September 2014 Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests Demonstrators surround cars and block roads on 28 September 2014 Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests Police use pepper spray as they clash with protesters jamming the main street to the financial Central district outside the government headquarters in Hong Kong on 28 September 2014 Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests Protesters wear masks and goggles to protect themselves from pepper spray while blocking a police car outside the government headquarters on 28 September 2014 AP In pictures: Hong Kong democracy protest 2014 Hong Kong protests Hong Kong media tycoon and pro-democracy supporter Jimmy Lai attends a rally near the government headquarters in Hong Kong on 28 September 2014 AFP In pictures: Hong Kong democracy protest 2014 Hong Kong protests The sign for the Hong Kong central government offices is seen crossed out on 28 September 2014 In pictures: Hong Kong democracy protest 2014 Hong Kong protests Policemen stand behind a fence decorated with yellow ribbons during a demonstration on 28 September 2014 AFP In pictures: Hong Kong democracy protest 2014 Hong Kong protests Hong Kong's Chief Executive Leung Chun-ying (C) and Chief Secretary Carrie Lam (R) attend a press conference in Hong Kong on 28 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Food and beverages are provided free to protesters during a demonstration outside the government headquarters in Hong Kong on 28 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Protestors tie up barricades during a demonstration outside the headquarters of the Legislative Counsel on 28 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Thousands of protesters attend a rally outside the government headquarters in Hong Kong as riot police stand guard on 27 September 2014 Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests Students demonstrate against China's decision not to allow a completely free election in Hong Kong in 2017 EPA In pictures: Hong Kong democracy protest 2014 Hong Kong protests Protesters are dragged away by police after storming into government headquarters in Hong Kong on 27 September 2014 Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests Protesters clash with riot police in Hong Kong on 27 September 2014 Getty In pictures: Hong Kong democracy protest 2014 Hong Kong protests Students and police clashed in demonstrations against China's decision not to allow a completely free election in Hong Kong in 2017 on 27 September Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests A protester holds up placards which reads "Occupy Central" (L) and "Civil Disobedience" (R) Reuters In pictures: Hong Kong democracy protest 2014 Hong Kong protests Protesters chant slogans in front of the police Reuters

But he added: “If he doesn't resign by tomorrow we will step up our actions, such as by occupying several important government buildings.”