Demonstrators flooded a park in central Hong Kong, chanting "Resist Beijing, Liberate Hong Kong" and "Stand with Hong Kong, fight for freedom." Many of them, clad in black shirts and wearing masks, waved American flags and carried posters that read "President Trump, please liberate Hong Kong" as they marched to the U.S. Consulate nearby.
"Hong Kong is at the forefront of the battle against the totalitarian regime of China," said Panzer Chan, one of the organizers of the march. "Please support us in our fight."
Hong Kong has been rocked by three months of unrest sparked by a proposed law that would have allowed criminal suspects to be sent to mainland China for trial. Many saw the extradition bill as a glaring example of the erosion of civil liberties and rights promised under a "one country, two systems" framework when the former British colony returned to Chinese rule in 1997.
The unrest has become the biggest challenge to Beijing's rule since Hong Kong's return from Britain. Beijing and the entirely state-controlled media have portrayed the protests as an effort by criminals to split the territory from China, backed by hostile foreigners.
Protesters on Sunday urged Washington to pass a bill, known as the Hong Kong Democratic and Human Rights Act, to support their cause. The bill proposes sanctions against Hong Kong and Chinese officials found to suppress democracy and human rights in the city, and could also affect Hong Kong's preferential trade status with the U.S.
A group of protesters sang "The Star-Spangled Banner" before handing over an appeal letter to a U.S. Consulate official.
Just before the rally ended, violence erupted after riot police detained several people and cleared a crowd from the nearby Central subway station. Angry protesters smashed glass windows, sprayed graffiti and started a fire at one at the station's exits.
The government said protesters also set street fires and blocked traffic at some thoroughfares. In the type of cat-and-mouse battle that has characterized the summer-long protests, riot police pursued groups of protesters down streets, but they kept regrouping.
Police fired multiple rounds of tear gas in the Causeway Bay shopping area after protesters heckled them and refused to leave. They also searched dozens of young people on the street and inside subway stations.
At the Mong Kok police station, clashes took place for a third straight night. Police fired projectiles at an angry crowd that was shining laser beams, and several people were detained.
The U.S. State Department said in a travel advisory Friday that Beijing has undertaken a propaganda campaign "falsely accusing the United States of fomenting unrest in Hong Kong." It said U.S. citizens and embassy staff were targeted and urged them to exercise increased caution.
Some American legislators are pressing Trump to take a tougher stand on Hong Kong. But the president has suggested that it's a matter for China to handle, though he also has said that no violence should be used. Political analysts suggest that Trump's response has been muted because he doesn't want to disrupt talks with China over their tariff war.
U.S. House Speaker Nancy Pelosi said in a statement Wednesday that Hong Kong residents deserve real autonomy and freedom from fear. She urged an end to police violence against protesters and said Congress looks forward to "swiftly advancing" the Hong Kong bill.
The protests are an embarrassment to China's ruling Communist Party ahead of the Oct. 1 celebration of its 70th anniversary in power.
Separately, well-known Hong Kong activist Joshua Wong said in a statement through his lawyer that he was detained at the city's airport early Friday for breaching bail conditions. Wong, a leader of Hong Kong's 2014 pro-democracy protest movement, was among several people detained last month and was charged with inciting people to join a protest in June.
Wong had just returned from Taiwan, where he gave speeches on Hong Kong's protests, and is due to visit Germany and the U.S. He said a court had approved his overseas trips.
He described his detention as a procedural hiccup and said he expected to be released Monday. His prosecution comes less than two months after his release from prison for a two-month sentence related to the 2014 protests.
Associated Press writer Joe McDonald in Beijing contributed to this report.