BEIJING -- China's top legislature took the rare step Monday of intervening directly in a local Hong Kong political dispute by effectively barring two legally elected separatist lawmakers from taking office, setting the stage for further turmoil in the semiautonomous city.

Beijing moved to deny the two a second chance to take their oaths after being disqualified on their initial attempt last month for using anti-China insults and foul language. But the manoeuvr circumvented Hong Kong's courts, raising fears that the city's independent judiciary is being undermined.

The decision was intended to nip in the bud the rise of separatist sentiment, but it has raised the spectre of more political unrest in Hong Kong. Major street demonstrations two years ago failed to win greater democracy but spawned an independence movement.

On Sunday, thousands rallied against the anticipated, Chinese government announcement. Police used pepper spray and batons against demonstrators trying to reach Beijing's liaison office. Four people were arrested and two officers were injured, police said.

The dispute centres on pro-independence lawmakers Sixtus Leung, 30, and Yau Wai-ching, 25, who altered their oaths to insert a disparaging Japanese expression for China. Displaying a flag reading "Hong Kong is not China," they vowed to defend the "Hong Kong nation." Their oaths were ruled invalid and subsequent attempts have resulted in mayhem in the Legislative Council's weekly sessions as the council's president refused to let them try again until the government's legal challenge is settled.

But Beijing decided to act more quickly. The National People's Congress Standing Committee, the country's top legislative panel, issued a ruling on a section of Hong Kong's Basic Law, or mini-constitution, covering oaths taken by officials. It said talk of independence for Hong Kong is intended to "divide the country" and that those who advocate independence are disqualified from election.

It's the first time Beijing has stepped in to block elected Hong Kong lawmakers from taking office, or has interpreted the Basic Law before a Hong Kong court has delivered a ruling on a case.

"For the young people this is going to definitely create a backlash. This is going to further fuel the independence movement," said Samson Yuen, a politics lecturer at the Open University of Hong Kong. He added that protests and collective action have hit a dead end.

"Rationally for young people the only way out is to fight more radically," he said.

The U.S. State Department expressed disappointment over Monday's developments and voiced strong support for Hong Kong's Legislative Council and independent judiciary.

"We believe that an open society with the highest possible degree of autonomy and government by the rule of law is essential for Hong Kong's continued stability and prosperity," spokesman Mark Toner told reporters in Washington.

In Beijing, Li Fei, a deputy secretary general of the NPC Standing Committee, denied that the central government was escalating its interference in Hong Kong's affairs.

He told reporters that the Basic Law stipulates that Beijing holds the legal power to make interpretations, and it is the central government's duty to step in when there is a difference of legal opinion. He also warned that promoting independence was not a matter of freedom of speech.

"Breaking 'one-country two-systems' is violating the law, not voicing a political view," said Li, referring to a principle under which Beijing is supposed to let Hong Kong keep its capitalist economic and political system separate from mainland China's until 2047.

The central government's stance is absolute, he said, adding, "There will be no leniency."

Ming Sing, a professor of social science at the Hong Kong University of Science and Technology, said Beijing was making a "disproportionate" response to the threat of a separatist movement, given that polls show an overwhelming majority of Hong Kong citizens do not support breaking away from China.

Eddie Chu, an independent pro-democracy lawmaker, said Beijing was making a "needless intervention" because Hong Kong's courts could have handled the dispute. He said Beijing was trying to deter those seeking greater self-determination for the city.

Chu is also among a group of pro-democracy candidates, also including Leung and Yau, who were elected for the first time in September. Leung and Yau are members of the radical Youngspiration party. They did not respond to media requests for comment Monday.

Hong Kong's Beijing-backed leader, Chief Executive Leung Chun-ying, said the government will fully implement the standing committee's interpretation. He said the duo had not only advocated independence, but "even insulted the country and the Chinese people in their words and deeds."

In Beijing, Li decried the two as "traitors" and recounted Japanese World War II atrocities in Hong Kong in graphic detail, telling of nurses raped and bodies bayoneted and tossed into the Hong Kong harbour.

"I hope the people of Hong Kong won't forget the history of Japanese invaders," he said. "All the traitors who sell out the country never have good endings."

------

Chan reported from Hong Kong. Associated Press journalists Gillian Wong in Beijing and Josie Wong in Hong Kong contributed to this report.