One opposition politician unfurled a banner from a balcony of the legislative council building saying the city's leader Carrie Lam "was corrupting Hong Kong and hurting its people; She will stink for 10,000 years."

"I suppose this is my last protest in Legco," opposition member Lam Cheuk-ting said after suspending the banner from the building's second floor. Chief Executive Carrie Lam was not in the assembly at the time.

Hong Kong's Beijing-backed government expelled four opposition members from the 70-seat Legislative Council, known as Legco, on Wednesday, saying they had threatened national security. The 15 remaining opposition lawmakers then said they would hand in their resignation letters in solidarity on Thursday.

The government disqualified the four legislators — Alvin Yeung, Dennis Kwok, Kwok Ka-ki and Kenneth Leung — after a resolution passed this week by China's parliament gave city authorities new powers to curb dissent. It cleared the way for the government to act against lawmakers seen as endangering national security, supporting Hong Kong independence, or refusing to acknowledge China's sovereignty over the city. Beijing imposed a controversial national security law in June after months of anti-government protests in the city last year.

Critics say the measure seeks to curtail the freedoms China promised Hong Kong could keep after the end of British colonial rule in 1997.

The departure of the opposition from the city's legislature has raised concerns about China's expanding control over the former British colony. It would essentially make it possible for Beijing loyalists, who already dominate the chamber, to pass laws favored by China with little opposition.