Hong Kong — Violence erupted between Hong Kong police and pro-democracy protestors outside a main government building on Sunday, as protestors defied a police ban by marching through the central business district.

Police fired chemical-laced blue water and tear gas at protesters who lobbed Molotov cocktails outside the Hong Kong government office complex Sunday. A mixed crowd of protesters clad in black and wearing masks — along with families with children — spilled into the roads of the Causeway Bay shopping belt and marched for over 1.2 miles to the central business district.

Police had turned down a request by the Civil Human Rights Front to hold the march, but the demonstrators were undeterred, as they've been all summer. Some waved U.S. and British flags, while others carried posters reiterating their calls for democratic reforms.

Anti-government protesters are sprayed by a water cannon during a demonstration near Central Government Complex in Hong Kong, Sunday, Sept. 15, 2019. Kin Cheung / AP

"I feel this is our duty. The government wants to block us with the ban, but I want to say that the people will not be afraid," said one protester, Winnie Leung, 50.

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Monday marked the end of the third straight month in Hong Kong's "summer of protest." Over the weekend, thousands of people hit the streets again — this time parading American flags and singing the U.S. National Anthem in hopes of getting Washington's attention.

Many Hong Kongers want the U.S. Congress to take up and pass the "Hong Kong Human Rights and Democracy Act," which would punish officials in Hong Kong and mainland China if they suppress liberties and freedoms in the semi-autonomous Chinese city. The Asian financial hub, known for its stability and economic growth during the past half-decade, has been in the throes of the worst chaos and violence it's seen in modern memory. A controversial China extradition bill first lit the match of anger that has exploded into million-person marches and the "five demands" made by the pro-democracy movement.

Sunday's march disrupted traffic and many shops closed their doors. Protesters burned Chinese flags and tore down banners congratulating China's ruling Communist Party, which will celebrate its 70th year in power on October 1.

A Pro-China supporter, center, is escorted by police after confronting journalists in north point, Hong Kong, Sunday, Sept. 15, 2019. Vincent Yu / AP

The protests were triggered in June by an extradition bill that many saw as an example of China's increasing intrusion and at chipping away at Hong Kong residents' freedoms and rights, many of which are not accorded to people in mainland China.

Hong Kong's government promised this month to withdraw the bill, which would have allowed some criminal suspects to be sent to mainland China for trial, but protesters have widened their demands to include direct elections for the city's leaders and police accountability.

More than 1,300 people have been arrested amid increasing clashes between protesters and police, who demonstrators have accused of abuses.

Earlier Sunday, hundreds of protesters waved British flags, sang "God Save the Queen" and chanted "U.K. save Hong Kong" outside the British Consulate as they stepped up calls for international support for their campaign. With banners declaring "one country, two systems is dead," they repeated calls for Hong Kong's former colonial ruler to ensure the city's autonomy is upheld under agreements made when Britain ceded power to China in 1997.

CBS News' Ramy Inocencio and Erin Lyall contributed to this report