The protest in the town of Sheung Shui is the latest in a string of demonstrations that has roiled the former British colony for more than a month, fueling its biggest political crisis since China regained control in 1997.
Street protests have drawn in millions, with hundreds even storming the legislature on July 1 to oppose the now-suspended extradition bill that would have allowed criminal suspects in Hong Kong to be sent to China to face trial.
Critics see the bill as a threat to Hong Kong's rule of law. Chief Executive Carrie Lam this week said the bill was "dead" after having suspended it last month, but opponents vow to settle for nothing short of its formal withdrawal.
Most protests centred on the central business district, but demonstrators have recently begun to look elsewhere to widen support by taking up narrower, more domestic issues.
Similar protests have included a march last week by nearly 2,000 people in the Tuen Mun residential district to protest against what they saw as the nuisance of brash singing and dancing to Mandarin pop songs by middle-aged mainland women.
On Sunday, tens of thousands marched in one of Kowloon's most popular tourist shopping areas, trying to persuade mainland Chinese tourists to back opposition to the extradition bill.
When former colonial ruler Britain returned Hong Kong to China in 1997, Chinese Communist leaders promised the city a high degree of autonomy for 50 years.
But many say China has progressively tightened its grip, putting Hong Kong's freedoms under threat through a range of measures such as the extradition bill.
Anti-extradition protesters plan another demonstration on Sunday in the town of Sha Tin, in the so-called New Territories between Hong Kong island and the border with China.