Hong Kong police fired tear gas on Sunday morning at protesters intent on keeping their stranglehold on a major tunnel as pro-democracy activists vowed to "squeeze the economy" into next week.
Hardliners occupying Hong Kong Polytechnic University in Kowloon -- now a key battleground near the blocked Cross Tunnel Harbour -- responded by throwing Molotov cocktails shortly before 10.30 am.
Dozens of government supporters had gathered in the area earlier to clear barricades near the university campus, which was the scene of more violence overnight as riot police clashed with protesters.
Around 80 to 100 middle-aged residents clapped and cheered as they moved debris from the road near the entrance to the crucial Cross Harbour Tunnel to Hong Kong island -- shut since Tuesday -- before protesters in masks and their signature black t-shirts returned to rebuild the roadblock.
Local media reported the activists were throwing bricks at the residents. The clashes broke out as demonstrators vowed online to continue their "Blossom Everywhere" campaign of blockades and vandalism across the semi-autonomous financial hub which last week shut down large chunks of the train network and forced schools and shopping malls to close.
A poster circulating on social media called for "dawn action" on Monday. "Get up early, directly target the regime, squeeze the economy to increase pressure," it said.
Students and protesters last week occupied several major universities around the city -- the first time a movement characterised by its fluidity and unpredictability has coagulated in fixed locations.
The Polytechnic University (PolyU) has become a major flashpoint in the city rocked by a week of intensified violence and chaos. A message on the university's Facebook page urged demonstrators to leave "immediately".
"In view of safety concerns posed by possible violent unlawful activities conducted by protesters who are still occupying the PolyU campus, the University again urges all people on campus, including students and staff members, not to stay, and to leave as soon as possible," the post said.
Chinese People's Liberation Army soldiers -- based in barracks near Hong Kong Baptist University -- briefly came out on Saturday to help the clean-up after a week of disruption, a rare and highly symbolic troop movement unsolicited by the city's embattled government.
The action saw scores of soldiers from the garrison, which is confined to the barracks under Hong Kong's mini-constitution, with crewcuts and identical gym kits conduct a lightning-quick removal of bricks and debris near their base.
Chinese state media has repeatedly warned that troops could be deployed to quell an unprecedented crisis in the semi-autonomous city that has entered its sixth month.
Confirming the brief deployment, the PLA said it acted to open a debris-strewn road outside their Kowloon Tong barracks to traffic, winning "applause from residents" in the process.
The last time soldiers assisted in the city was in 2018 to clean up after a typhoon.
A spokesman for Hong Kong's government said the troop movement had not been requested by city authorities but was instead a "voluntary community activity initiated by themselves".
The protests started against a now shelved bill to allow extradition to China but have billowed into wider calls for democracy.
Two people have died this month as the violence worsened, while the financial hub has been pushed into a recession by the turmoil.