Students fought running battles with police outside government headquarters on Sunday night as Occupy protesters tried to storm the Admiralty compound and lay siege to Chief Executive Leung Chun-ying's office. Minutes after student leaders called on the thousands gathered at the Admiralty Occupy encampment, hundreds of protesters - wearing an assortment of hard hats and protective masks - thronged around government headquarters and Tamar Park and began trying to breach police lines at various points. Police used pepper spray and baton charges to repel them, leaving some bloodied and requiring treatment by makeshift medics. Key areas of violence were Lung Wo Road and the walkways from Harcourt Road to government headquarters. Watch: Occupy protesters clash with police in Admiralty as movement escalates At the same time, fresh trouble flared in Mong Kok as police and protesters clashed, although the disturbances subsided after 10 or so minutes, leaving the situation tense. The renewed violence came after police had earlier warned of resolute action to prevent any such blockade, while Federation of Students leaders told activists to avoid “giving the police a legitimate reason to take violent actions” as they stepped up the protests. In a statement at 10.20pm, police “strongly condemned” the “unlawful assemblies in Admiralty for storming police cordon lines and obstructing roads”. Vowing to use “suitable force resolutely”, they urged protesters to “stay away from radicals and troublemakers”. Police issued a second statement an hour later urging organisers of Occupy to end their “illegal” actions. A spokesman said the violent charging of police cordons had deviated from the movement’s non-violent principle as claimed by the organisers. The Heads of Universities Committee last night to remain calm and be rational. “Please do not take part in any attack against the government headquarters,” it said in a statement. “Stay away from areas where there are clashes. Evacuate from the site immediately if your personal safety is in danger. Please contact your respective institution for help if needed.” The escalation, rumoured for much of the weekend, was announced at 9pm on the main stage, when federation representative Nathan Law Kwun-chung urged people to head towards the government offices. He said there would be a “long journey” through the night, and called on Hongkongers to “walk” with them. Soon afterwards, supporters began streaming towards the government offices on Tim Mei Avenue. Soon after, police in riot gear raised warning signs in Tamar Park telling protesters to “stop charging”. Hours earlier, police warned the public against attending a rally called by the federation in the protest zone. About 3,000 officers were posted in Admiralty, with a further 4,000 in Mong Kok, where protests have continued despite the clearance of the main protest zone last week. Describing the rally as posing an “extremely high risk”, Senior Superintendent Kong Man-keung of the police’s public relations branch warned the public against attending. He said student leaders had urged people to bring supplies to the site. “I emphasise that if anyone obstructs the police in execution of their duty, charge the police line violently, or attempt to block the central government office, police will take resolute enforcement actions,” Kong said. Oscar Lai Man-Lok, spokesman for student group Scholarism, said the crowd was the biggest in at least two weeks. He told protesters to stick to their non-violent principles and not to provoke or charge at police. Among those present, there was support for the idea of stepping up the campaign. Hin Kan, a university student, said he felt the night's action was "encouraging". "Unlike the guerrilla warfare in Mong Kok, we have here demonstrated a clear goal of blockading the government headquarters by storming the different access routes. This is a clear action demanding the government to respond to our call for universal suffrage." "Maybe we will lose tonight, but the call for democracy had taken root in our hearts." “The government has not responded to our demands yet, so we have to do something,” said Gary Wu, 24, an advertising worker. “I support their plan to escalate their action ... But if it is to stop all civil servants from going to work, it will affect people’s livelihoods and I have reservations,” said another protester. Kevin Suen, also a university student, said: “How ironic. Christmas lights are shining but here we stand fighting for universal suffrage.” He said he was not afraid of the police. “Two months on, I’ve got used to the pattern. we advance, police use pepper spray or batons and we step back. Those behind then forward.” Schoolgirl Fish Chan, 16, said she had attended despite being urged to stay away by her mother, who feared she would be hurt. Earlier, a group of secondary school pupils staged a barefoot walk around the government headquarters. They knelt down after every 28 steps and walked around the buildings nine times to remember the police’s use of tear gas on September 28. A former student leader exiled from the mainland after the bloody Tiananmen Square crackdown told RTHK today that he feared there would be bloodshed at the Admiralty rally. In the event of violence, he said he would push for Hong Kong’s Chief Executive Leung to face an international court. Speaking in Taipei in his capacity as chairman of New School for Democracy, he said the school and other human rights groups would consider attempting to get Leung tried at the Hague International Court of Justice for crimes against humanity. "The violence the Hong Kong government used has already exceeded a standard acceptable in humanity," he said. Wang has been exiled since the 1989 Tiananmen democracy movement ended in a bloody military crackdown. A well-placed source close to the Federation of Students said their call for people to come prepared for escalated action - possibly by blocking the entrances and exits to government headquarters - would force the police to make arrests, sending the signal to those less radical diehards still encamped in Admiralty that it was time to leave. The strategy - which has not been finalised - flies in the face of the approach preferred by the core trio of older Occupy Central founders led by Benny Tai Yiu-ting, who plan simply to hand themselves in to the police in a bid to convince an increasingly sceptical public that they don't want to flout the rule of law. The founding trio of Occupy - Tai, Chan Kin-man and the Reverend Chu Yiu-ming - are set to surrender to police on Friday after ditching a plan to do it today because "they want to stay until the end of the fight", according to a source close to that camp. "The three co-founders once considered surrendering earlier than their scheduled date - December 5 - to avoid a confrontation, but in the end they scrapped the idea as others want them to stay until the end of the fight," the source said. The student leaders, however, hope that being arrested amid a police crackdown on escalated action would prompt protesters to rethink how the movement should proceed. "It is a common belief of organisers that it is time to get off the streets and take the campaign for democracy forward to a more sustainable format," said a source close to the inner core of the Federation of Students. "Surrounding government offices would prompt police to take action, and it is hoped that the protesters will start thinking about how to carry on the movement elsewhere, without occupying." Federation of Students secretary general Alex Chow Yong-kang had earlier called on protesters to get back to Admiralty today with their "safety equipment" such as umbrellas and goggles. "It could be another turning point" for the movement, he said on Friday, without disclosing any concrete details. Meanwhile, a group of journalists and members of the public filed reports at the police headquarters en masse yesterday regarding officers' recent alleged assaults on journalists. The move by the members of five local journalists' groups came after a NOW TV engineer and an Apple Daily videographer were arrested while covering events at the Mong Kok protest site over the past week. Other groups that also reported to the police collectively included the Hong Kong Journalists Association, the RTHK Programme Staff Union, Next Media Trade Union and Journalism Educators for Press Freedom. A group of British lawmakers investigating the UK’s relations with Hong Kong have been told China will not allow them into the former colony, Agence France-Presse reported. The Foreign Affairs Committee, a panel of lawmakers who scrutinise the Foreign Office’s work, is looking into Britain’s relations with Hong Kong 30 years on from the 1984 Joint Declaration, which set out the terms of the 1997 handover of Hong Kong. Richard Ottaway, who chairs the cross-party panel, said he would on Monday call for an emergency debate in parliament on the situation. The 11-member committee, which reports to the lower House of Commons, planned to visit Hong Kong before the end of the year as part of its inquiry. “The Chinese government have, in past weeks and months, registered their opposition to the inquiry,” the committee said in a statement. “I have been informed by the Chinese embassy that if we attempt to travel to Hong Kong we will be refused entry,” Ottaway said. “We are a committee of elected members of parliament from a democratic nation who wish to scrutinise British diplomatic work in Hong Kong. “The Chinese government are acting in an overtly confrontational manner in refusing us access to do our job. “I shall be asking the speaker tomorrow to grant an emergency debate on the floor of the house,” he said. Earlier this month, the panel questioned Chris Patten, the governor who oversaw the transfer of Hong Kong from British to Chinese sovereignty. He rejected Beijing’s assertions that Hong Kong’s political situation was no longer anything to do with London, citing binding agreements signed between the countries. “The Joint Declaration provides obligations on China to us for 50 years,” he said.