Public broadcasting service RTHK has reported that people started protesting in Mong Kok at 12:00 GMT. The police detained two people during the rally, which raised the crowd's ire. A few hours later the police hoisted a black flag and started dispersing protesters with tear gas, the media outlet said.
Hong Kong has been gripped by violent protests since June. The demonstrations, initially a response to an extradition bill, continued even after the highly unpopular measure was withdrawn in October. The protesters now claim that the authorities are abusing their power to suppress them, a claim that the government has denied.
Beijing views the situation in Hong Kong as a result of foreign interference in China's domestic affairs and expresses full support for the local authorities.