TVB said one of its reporters and a cameraman suffered injuries to their faces and hands.
The police said officers were also burned by the fluid which they said had been thrown by “rioters”.
The force posted photos on social media showing an officer with injuries to his chest, and holes burned through a police uniform.
The police said they strongly condemned the violent acts and appealed to the public to watch out for their personal safety.
The incident came as a large group of protesters battled riot officers outside Tuen Mun Town Hall, with the police forced to retreat until reinforcements arrived.