Hong Kong police fired tear gas to disperse violent protesters after they set fire to a national flag, damaged public property and hurled petrol bombs in Tuen Mun area. 

Police had earlier warned the protesters on Twitter that they would conduct an operation to stop the violence. The protesters also vandalized facilities of the Tuen Mun Light Rail Station, disrupting traffic in the city. 

The protest was held after pro-government groups pulled down anti-government messages from public walls.