HONG KONG — Hong Kong was bracing for further unrest on Sunday, a day after some Chinese troops left their barracks and staged a rare, tightly choreographed cleanup of streets that antigovernment protesters had filled with bricks during the week.
The brief photo op by China’s People’s Liberation Army — coupled with a continuing police operation on Sunday against students occupying a university campus — threatened to upend a fragile calm that had returned to the Chinese territory after a workweek marred by protests, transit disruptions and street violence.
The Chinese soldiers jogged out of their barracks on Saturday in Kowloon Tong, an upscale neighborhood, and cleared bricks from streets outside a university that had been swarmed by young demonstrators earlier in the week. The soldiers wore T-shirts and basketball jerseys, rather than military uniforms, and carried brooms instead of weapons.
The P.L.A.’s propaganda stunt appeared designed to tap into a desire among many Hong Kong residents for a semblance of order after a particularly intense week of unrest. But it threatened to inflame tensions in a semiautonomous Chinese territory where many are deeply sensitive about what they see as Beijing’s growing influence over their lives.
The stunt unfolded during a weekend when police officers were attempting to clear protesters who had occupied Hong Kong Polytechnic University, which is south of Kowloon Tong, and blockaded a nearby harbor tunnel. Demonstrations were also planned on Sunday in the city’s financial district.
The Hong Kong protests started in June over legislation, now withdrawn, that would have allowed extraditions to mainland China, where the courts are controlled by the ruling Communist Party. They have since expanded to include a broad range of demands for police accountability and greater democracy.
The Hong Kong garrison of the People’s Liberation Army is based in 19 sites once occupied by the British military before the former colony returned to Chinese control in 1997. Estimates of the number of Chinese troops stationed in the city vary from about 6,000 to 10,000.
British soldiers were frequently on the streets of Hong Kong before the 1997 handover, but it is highly unusual for Chinese troops to leave their Hong Kong barracks. One exception came last year, when hundreds of uniformed soldiers helped with cleanup efforts after a typhoon battered the city.
The H.K.B.U. protesters had spent days barricading roads, making gasoline bombs and engaging in standoffs with the police — steps from the garrison’s barbed wire fences. The university is one of several in Hong Kong that have canceled on-campus classes for the remainder of the fall semester.
The cleanup on Saturday lasted less than an hour and seemed designed to play to a mainland China audience. The Global Times, a nationalist tabloid, said in an English-language tweet that the soldiers had “perfectly cleaned” up the streets and “cleared the mess left by rioters.”
The mini-constitution that has governed Hong Kong since 1997 says that P.L.A. forces “shall not interfere” in local affairs, and that the local government may ask for the army’s assistance for disaster relief and maintaining public order. The Hong Kong government said in a statement on Saturday that the soldiers’ cleanup in Kowloon Tong was a self-initiated “community activity.”
But the move prompted a torrent of criticism from Hong Kong residents. On Saturday, 24 lawmakers in the city’s pro-democracy legislative minority issued a joint statement saying that the government and the P.L.A. had ignored restrictions imposed on the troops by local laws.
“They want the Hong Kong people to get used to the P.L.A.’s public activities in Hong Kong and gradually rationalize the P.L.A.’s operations in Hong Kong,” the lawmakers wrote.
Ezra Cheung, Katherine Li and Keith Bradsher contributed reporting.