Four opposition pro-democracy lawmakers in Hong Kong have been disqualified with immediate effect.

The expulsion came moments after Beijing passed a resolution allowing for the disqualification of lawmakers found to have supported the city's independence.

The move is being seen as the latest attempt by China to restrict Hong Kong's freedoms.

Other pro-democracy lawmakers are expected to resign in protest.

What does the resolution say?

The new resolution passed by China's National People's Congress Standing Committee says that lawmakers should be disqualified if they support Hong Kong independence, refuse to acknowledge China's sovereignty, ask foreign forces to interfere in the city's affairs or in other ways threaten national security.

It also allows Hong Kong government to directly remove lawmakers without having to approach the courts.

It comes after China in late June introduced a controversial and far-reaching national security law in Hong Kong that criminalised "secession, subversion and collusion with foreign forces".

The law was introduced after years marked by waves of pro-democracy and anti-Beijing protests. It has already led to several arrests of activists and has largely silenced protesters.

Who has been disqualified?

The four unseated lawmakers are Alvin Yeung, Kwok Ka-ki and Dennis Kwok of the Civic Party and Kenneth Leung of the Professionals Guild.

"If observing due process, protecting systems and functions and fighting for democracy and human rights would lead to the consequences of being disqualified, it would be my honour," Dennis Kwok, told reporters shortly after the news..

They were among 12 legislators who were earlier barred from standing in a legislative election before the polls were postponed to next year.

The group had called on US officials to sanction those responsible for alleged human rights abuses in Hong Kong.

The city's pro-democracy legislators have 19 seats in the 70-seat legislature.

What reasons are being given for their removal?

Speaking to the media, Hong Kong's top official, Chief Executive Carrie Lam said the four council members that were disqualified had already been found to not fulfil the requirements to stand in the now-postponed elections next year.

She added that although she "welcomes diverse opinions in the Legislative Council" these had to be expressed "in a responsible manner".

All members would have to be in line with the territory's mini constitution, the Basic Law, and other local legislation including the new national security law, she said.

"We could not allow members of the Legislative Council who have been judged not to fulfil the requirements to serve in the Legislative Council, to continue to serve there."

She also dismissed concerns that a mass resignation of the remaining pro-democracy lawmakers would turn the Legislative Council into a "rubberstamp" body.

What is the background to this?

Hong Kong was a British colony until 1997 when it was returned to Chinese control.

Under the principle of "one country, two systems" the territory was supposed to maintain more rights and freedoms than the mainland until 2047.

As a Special Administrative Region, Hong Kong was to have its own legal system, multiple political parties, and rights including freedom of assembly and free speech.

In response to the security law - passed in response to months of pro-democracy protests - the UK has offered a route to British citizenship to residents still holding a British National Overseas (BNO) passport.

Around 300,000 people currently hold BNO passports, while an estimated 2.9 million people born before the handover are eligible for it.

China last month strongly criticised the UK in response, telling London to "immediately correct its mistakes".