Democracy activists in the financial hub had vowed to ramp up their nearly four-month-long campaign ahead of Tuesday's National Day celebrations, which Hong Kong protesters have dubbed a "Day of Grief".
Sunday witnessed the most intense clashes in weeks as police used tear gas, rubber bullets and water cannons at multiple locations for hours during running battles with hardcore protesters hurling rocks and petrol bombs. Using online forums and social media, demonstrators had called for "anti-totalitarian" rallies to be held around the globe.
Marches were held in Australia and Taiwan, with more planned in some 40 locations across Europe and North America later in the day. Clashes broke out before Hong Kong's unsanctioned march had begun after angry groups in the shopping district of Causeway Bay surrounded and heckled officers who were conducting stop and searches. But the tear gas fired by police only emboldened the crowds, who then began walking through the streets in their thousands.
Some activists vandalised subway stations, tore down banners proclaiming the upcoming 70th anniversary celebrations and set fire to makeshift barricades.
Over the last 17 weeks, Hong Kong has witnessed the worst political unrest since its handover to China in 1997 with huge pro-democracy rallies as well as increasingly intense clashes between police and a minority of violent protesters. The city's summer of discontent was first triggered by an extradition bill to the mainland that has now been shelved. But the movement has since morphed into a call for free elections and less intervention from Beijing.
On Friday and Saturday night, tens of thousands of people turned out for two peaceful rallies. But there were brief clashes on Saturday night when police used water cannon and tear gas to beat back small groups of protesters hurling bricks and petrol bombs at a government building.
Students are planning a one-day strike on Monday while activists have called for people to dress in black on Tuesday.