Communist Party mouthpiece Xinhua on Sunday condemned the increasingly violent anti-government protests in Hong Kong, warning that “the end is coming for those attempting to disrupt Hong Kong and antagonise China”. The news agency’s commentary did not threaten specific action to end the protests, other than repeating unwavering support for the Hong Kong government and police actions to end them. But the commentary – the latest in a series of strongly worded statements from Beijing – did lay out three bottom lines “that must not be crossed”. “No one should harm [China’s] national sovereignty and security; no one should challenge the power of the central authorities and the authority of the Basic Law of the HKSAR; no one should use Hong Kong to infiltrate and undermine the mainland,” it said, referring to the city’s formal title of Special Administrative Region. “Anyone who dares to infringe upon these bottom lines and interfere in or damage the ‘one country, two systems’ principle will face nothing but failure and will be held accountable by the country’s constitution and the HKSAR’s Basic Law.” The protest violence this weekend was some of the most intense since the unrest – sparked by a now-shelved extradition bill that would have allowed criminal suspects to be sent to mainland China for trial – began in early June. On Saturday, police and protesters clashed in the city centre , with demonstrators lighting fires and hurling petrol bombs at police, who responded with water cannon and tear gas. Riot police also chased protesters onto a subway train, with video footage showing officers beating people with batons and pepper spraying them. On Sunday, protesters tried to shut down the city’s airport for the third time in a month, erecting barriers from luggage carts and fencing to block the entrances. Police cordoned off the airport terminals, allowing only ticketed passengers through their barricades. After leaving the airport in the early evening, protesters ransacked the nearest subway station, destroying equipment and spray painting anti-government slogans on the walls. The commentary warned that the protesters would soon face justice. “Behind the violence and chaos in Hong Kong is an elaborate scheme of the rioters and their patrons whose real intent is clearly exposed now. They tried to stir up unrest in Hong Kong and compromise the one country, two systems principle, before spreading the ‘colour revolution’ into the Chinese mainland,” it said. “However, their attempt to kidnap Hong Kong and press the central authorities is just a delusion. No concession should be expected concerning [this] principle.” Xinhua first referred directly to the protests as a “colour revolution” – widely used to refer to uprisings in countries in Eastern Europe, North Africa and the Middle East in the early 2000s – in a commentary a week ago . In that commentary, the news agency quoted late Chinese leader Deng Xiaoping as having said in 1984 that the mainland government “should intervene” in the event of unrest in the city. However, it did not repeat the intervention reference in this Sunday’s commentary. Still, the message was clear that Beijing would not give in to the protesters’ demands in any way. “Faced with the central government’s resolute support for the HKSAR government and the Hong Kong police, faced with the HKSAR government’s firm and just law enforcement, faced with strong condemnation from Chinese people, the end is coming for those attempting to disrupt Hong Kong and antagonise China,” it said. “They should never misjudge the determination and ability of the central government, the HKSAR government and Chinese people to safeguard the nation’s sovereignty, security and core interests.” It came after political heavyweights at a seminar in Shenzhen last weekend said Beijing had the right to intervene to resolve the crisis in Hong Kong and that mobilising PLA troops to do so would not bring an end to one country, two systems. Speaking at the same seminar, Xu Ze, head of the semi-official Chinese Association of Hong Kong and Macau Studies and a former director of the Hong Kong and Macau Affairs Office, said the city risked “sinking into an abyss”, and described the unrest as “a decisive battle between defending or destroying one country, two systems”. China’s state media has stepped up its attacks on the Hong Kong protests, with recent articles taking aim at pro-democracy figures including Hong Kong’s former chief secretary Anson Chan Fang On-sang, former lawmakers Martin Lee Chu-ming and Albert Ho Chun-yan, and media tycoon Jimmy Lai Chee-ying for “bringing ruin to Hong Kong”. Hu Xijin, editor-in-chief of nationalistic tabloid Global Times , last week warned of “catastrophic” consequences if the city did not stop itself from becoming a battleground between Beijing and Washington. He said that while the unrest was mainly the result of domestic factors, “aiding and abetting” by the US and other Western countries made de-escalation difficult.