A pro-Beijing group has filed a police report over alleged cyber-bullying against lawmaker Junius Ho.
The Defend Hong Kong Campaign also staged a rally in Wan Chai to show their support for Ho.
The protesters alleged that some social media users posted messages saying they hoped the lawmaker and his family would die or end up in a coma.
The protesters also called for an investigation into online entries that allegedly promote Hong Kong independence.
Ho had provoked an outcry last week by saying advocates of Hong Kong’s independence should be killed.
He later defended his words, saying his words in Chinese meant "halt" independence advocates rather than kill them.