Tear gas was first fired at about 5:20 p.m. local time (09:20 GMT), the South China Morning Post reported.
Thousands of protesters earlier in day took to the streets of Yuen Long, a town in the northern New Territories of Hong Kong, despite a police ban. The crowds are also protesting against attacks by triad members and local villagers.
Tear gas was first fired at about 7:20 p.m. local time (09:20 GMT), the South China Morning Post reported.
Several people reportedly received injuries in clashes with the police. At least one man was detained, the newspaper added. The police are calling on the crowd to disperse as the protest is illegal. The protesters, meanwhile, have broken a police bus with police officers inside and a car parked in the area.
Mass rallies erupted in Hong Kong in early June as the authorities were considering adopting a bill that would allow the autonomous Chinese city to extradite suspects to jurisdictions with which it did not have an extradition agreement, including mainland China.
Pressured by the protests, the government indefinitely suspended the bill, while Hong Kong Chief Executive Carrie Lam issued a public apology. However, the protesters still demand the complete withdrawal of the extradition amendments.
During a rally last Sunday, unknown suspects armed with wooden sticks and metal rods attacked passengers at the Yuen Long subway station injuring about 50 people.