Hong Kong (CNN)Thousands of pro-democracy protesters returned to the streets of Hong Kong Sunday, less than 24 hours after an initially peaceful demonstration descended into violence, the latest confrontation amid a deepening political crisis.A protester throws tear gas back at police officers during a demonstration in the district of Yuen Long in Hong Kong on July 27, 2019. More violence in Yuen Long Sunday's protest comes a day after riot police and protesters clashed in the small town of Yuen Long, near Hong Kong's border with China. Police had declined to grant the protesters a letter of no objection, owing to safety concerns, and classified the march as an unauthorized assembly. Yuen Long has become an unlikely focal point of the city's pro-democracy movement after protesters returning to the town from a march in downtown Hong Kong, that police had broken up Sunday, July 21, were viciously attacked by a mob wielding iron bars and bamboo sticks. About a dozen men have been arrested in connection with that attack, some of whom have links to organized crime groups, or triads. Protesters were reportedly at the mercy of the mob for almost an hour before police arrived and at least 45 people were injured, some seriously. On Saturday, protesters, many wearing black, returned to the district, chanting "There is no riot only a tyranny" and "Hong Kong Police, the lawbreakers" as they thronged through the streets in sweltering summer temperatures. Police initially appeared unwilling to intervene, but as dusk approached, hundreds of officers in full riot gear advanced on demonstrators. The crowd quickly thinned, but a core of several hundred mostly young protesters in hard yellow helmets and protective gear, appeared unwilling to back down -- charging police lines and forming barricades. In response, police fired tear gas and rubber bullets at demonstrators, many of whom had armed themselves with improvised shields and sticks. A small group of front line protesters threw bricks and other materials at police as the two sides fought running pitched battles through the streets. As night fell, additional riot police advanced from multiple angles slowly pushing demonstrators in the direction of Yuen Long metro station, in a final bid to clear the streets. Chaos briefly reigned inside the station when riot police charged up the stairs with batons, hitting protesters and using pepper spray. Twenty four people between the ages of 15 and 60 were hospitalized following the clashes, authorities confirmed. Two were in a serious condition. In statement Saturday, Hong Kong police reiterated that the demonstration had been an "unauthorized assembly" and accused protesters of throwing bricks and "hard objects" at officers during violent clashes.