Police had not been seen during Saturday afternoon as tens of thousands of protesters marched through Mong Kok, usually a busy shopping district. But they charged onto the streets after 9 p.m. (1300 GMT), with hundreds of officers in riot gear pushing back crowds who jeered them.

At around midnight in Wong Tai Sin, a residential area, protesters hurled umbrellas and other objects at police, who responded with pepper spray and then tear gas.

Throughout the evening in Kowloon, police confronted protesters who retreated and regrouped. Some were detained.