Hong Kong is facing a severe political crisis after China barred two pro-independence politicians from the city's legislature. In a highly controversial move, Beijing said Yau Wai-ching and Sixtus "Baggio" Leung would not be able to hold office, striking a blow to the burgeoning movement calling for greater autonomy from the mainland. The ruling, which amounts to Beijing's most direct intervention in the territory's legal system since the 1997 handover to Chinese rule, is expected to spark renewed street protests in the former British colony. During a chaotic swearing-in ceremony last month, Yau and Leung thumbed their noses at Beijing by refusing to declare their allegiance to China and carrying blue flags reading: "Hong Kong is not China." The pair's oaths are invalid and they will not be able to retake them, China's rubberstamp legislature said, one day after thousands marched through the streets of Hong Kong to protest against Beijing's interference. Those wishing to hold public office must "sincerely and solemnly" declare allegiance to China, it said. Legislators must swear allegiance to "the Hong Kong Special Administrative Region of the People's Republic of China", according to the Basic Law, the city's mini-constitution. "Since the legislative council elections, some people have been advocating independence and saying they want to do it in Legco," Li Fei, the chairman of the Basic Law committee at China's parliament, said at a press conference announcing the decision. "The interpretation today will help to defend national unity and sovereignty." Any calls for "self-determination" amounted to advocating for independence, with both standing at odds with the Basic Law, Li added. He warned allowing independence talk to go unchecked would harm territorial integrity, national security and competitiveness. The Chinese government "is determined to firmly confront the pro-independence forces without any ambiguity," he added. The decision in unlikely to silence calls in Hong Kong for greater autonomy and independence Emily Lau, a veteran member of Hong Kong's pro-democracy camp, said Beijing had decided to intervene because it feared the spread of independence to regions such as Tibet and Xinjiang where there is longstanding resistance to the Communist party's rule. Lau, the chairwoman of Hong Kong's Democratic party, said that by preventing Leung and Yau from taking up their seats Beijing hoped to nip Hong Kong's independence movement in the bud. "But you can't nip it because there are many students in secondary schools and in universities who support the idea," she said. "So what Beijing should be asking is not so much, "How do we get rid of it?' It is, "How come our young people - and even those who are not so young - how come they advocate[independence]?'" "That is the way of solving the problem, not trying to suppress it. Because the harder you suppress, the more they will rise up," she added. Eddie Chu, a pro-democracy politician, said Beijing's intervention would only fuel greater opposition from young people who were increasingly disillusioned with its rule. "Every time Beijing tries to use legal instruments to stop Hong Kong people seeking democracy, the opposite will happen. More people, in particular young people, will be more determined in thinking about breaking through the restrictions set by Beijing," Chu said. "The thoughts of the young people have changed a lot in these few years and I don't think this interpretation will deter them from seeking self-determination. Quite the opposite." Chu said the ruling was the latest example of Beijing's meddling in what he described as Hong Kong's internal affairs. "It is like something happening on another planet - but it will have serious consequences for us," he warned. However, pro-China voices welcomed the ruling. Holden Chow, one of the rising stars of Hong Kong's pro-Beijing camp, said he backed the central government's "tough decision" to disqualify Yau and Leung from the legislative council, a move he claimed many in the former colony would welcome. Chow, a politician from Hong Kong's largest pro-Beijing party, the Democratic Alliance for the Betterment and Progress of Hong Kong (DAB), said there was no place for such voices in the legislature. "Their behaviour was blatant and notorious," he said of Yau and Leung. "When they took their oaths they used derogatory words to insult Chinese people and have been bluntly advocating the independence of Hong Kong." "Hong Kong is indeed part of China," Chow added. "If you deny that, why would you participate in the legislative chamber? Why would you insist on having a seat? ... Obviously, without their presence it will be better." Hong Kong's pro-democracy protests have been overwhelmingly peaceful but Chow said he feared that "some of the radicals" would stage "violent protests" in response to the decision. After the UK handed Hong Kong to China in 1997, the city maintained its own laws, courts and freedoms not enjoyed in mainland China, under a framework known as "one country, two systems". But many in Hong Kong complain those freedoms have been eroded in recent years, leading to nearly three months of street protests in 2014 - known as the umbrella revolution - and to the election in September this year of six politicians pushing for greater autonomy for the city. About 13,000 marched on Sunday to protest against China's intervention, ending in clashes with police outside Beijing's main presence in the city and four arrests. China's move to bar the two young legislators sets up a new battle between pro-Beijing and pro-democracy camps as a fresh round of elections will be held to replace Leung and Yau.