Hong Kong police fired tear gas in Mong Kok for the second night in a row, after a number of skirmishes between officers and anti-government protesters.

Rounds of tear gas were fired at about 12.45am on Monday on Portland Street in the popular entertainment and shopping hub after police said they came under attack.

“A large group of rioters gathering in Portland Street, Mong Kok behaved in a disorderly manner and disturbed public peace,” a police statement said.

“Despite repeated warnings by police, the rioters refused to leave, and after midnight, threw hard objects at police officers at the junction of Shantung Street and Portland Street.

“In the face of the situation, police officers have deployed tear gas to effect the dispersal of rioters, who are warned to stop all unlawful acts immediately.”

Earlier in the evening, tensions flared as protesters blocked roads, prompting riot police to arrive on the scene. Officers raised a black flag warning of the use of tear gas.

The force said passers-by were assaulted as protesters blocked roads, forcing the police’s intervention to clear the streets and unlock traffic jams.

“Around 9pm, rioters blocked roads and behaved in a disorderly manner at the junction of Nathan Road and Nelson Street, Mong Kok,” police said in a statement on Sunday evening.

“Some rioters even assaulted three innocent passers-by, taking the law into their own hands.

“Police warn all rioters to stop all unlawful acts and will take resolute enforcement actions.”

On Saturday, tear gas was fired on the first day of the Lunar New Year, as people gathered to mark the fourth anniversary of the Mong Kok riot of 2016.

Riot police presence grew early into the evening on Sunday outside the Langham Place shopping centre on Portland Street. Police had earlier entered the mall, following reports of a disturbance.

Just before 10pm, police raised the tear gas warning.

Street vendors donned masks but continued to sell fish balls and deep-fried tofu.

The scenes were similar to the first night of the Lunar New Year in 2016, which prompted the riots later dubbed the “fishball revolution”.

Four years ago on February 8, what started out as a dispute between vendors and crowd control officers rapidly escalated into a full-blown night of vandalism and arson, as a crowd led by pro-independence group Hong Kong Indigenous clashed with police.