A Hong Kong court on Tuesday ruled to disqualify two pro-independence lawmakers from parliament, a week after Beijing said it would not allow the pair to be sworn into office as fears grow of the city's liberties coming under threat.

Baggio Leung and Yau Wai-ching, who deliberately misread their oaths of office, inserted expletives and draped themselves with "Hong Kong is not China" flags during a swearing-in ceremony last month, said they would appeal the decision.

"Mr. Leung and Ms. Yau have been disqualified from assuming and have vacated the office of a member of the Legislative Council," judge Thomas Au said in a written judgement.

"The oaths purportedly taken by Mr. Leung and Ms. Yau on October 12 2016... are invalid and void and have no legal effect," Au said.

Au also said the way the democratically elected pair took their oaths showed "clearly that they did not truthfully and faithfully intend to commit themselves to uphold and abide by" the city's constitution.

Leung said they would appeal the ruling.

"The judgement simply reflects that elections in Hong Kong are meaningless and the result... can be easily overturned by the government," said Leung.

"We will go forward and appeal to the Court of Final Appeal if that is where we have to go to see justice served."

Yau had earlier told a media scrum outside the courthouse that the ruling did not come as a surprise.

"The government has used so many small acts to suppress the courts and the courts had so much pressure and came up with such a decision," she said.

Links to the pair's biographies were no longer accessible on the Legislative Council (Legco) website Tuesday evening.

- Zero tolerance -

The High Court's decision was preempted by Beijing's ruling last week, which said that any oath taker who does not follow the prescribed wording of the oath, "or takes the oath in a manner which is not sincere or not solemn", should be disqualified.

That move was slammed by pro-democracy activists and legal experts as a massive blow to Hong Kong's judicial independence and sparked demonstrations by both pro-Beijing and pro-independence groups.

"With or without (Beijing's) interpretation, the court would reach the same conclusion," Au said in the ruling.

However, political analyst Willy Lam said Beijing's interpretation would likely prevent pro-independence figures from running in future elections.

"The electoral commission now has full rights to disqualify like-minded people," Lam, a professor at the Chinese University, told AFP.

Ahead of the court ruling, the city's chief executive called for zero tolerance in dealing with activists pushing for independence from China.

"Members of the Hong Kong independence (movement) cannot appear in the political system," Leung Chung-ying said, describing the group as a small minority.

The unpopular leader on Tuesday said he welcomed the ruling and was mulling the next step, while Legco's president said it was up to Hong Kong's government to arrange a by-election to fill the seats.

Hong Kong was handed back to China by Britain in 1997 under a "one country, two systems" deal which protects its freedoms for 50 years, but there are growing concerns those liberties are disappearing.