Violent clashes erupted in Hong Kong early on Sunday for a second night, deepening a sense of impasse between a government with limited options and a pro-democracy movement increasingly willing to confront police.
The worst political crisis in Hong Kong since Britain handed the free-wheeling capitalist city back to China in 1997 entered its fourth week with no sign of a resolution despite talks scheduled for two hours on Tuesday between the government and student protest leaders.
Beijing has signalled through Hong Kong's leaders that it is not willing to reverse a decision in August that effectively denies the financial hub the full democracy the protesters are demanding.
"Unless there is some kind of breakthrough in two hours of talks on Tuesday, I'm worried we will see the standoff worsen and getting violent," Sonny Lo, a professor at the Hong Kong Institute of Education, told Reuters.
"We could be entering a new and much more problematic stage. I hope the government has worked out some compromises, because things could get very difficult now."
Hong Kong's 28,000 strong police have been struggling to contain a youth-led movement that has shown little sign of waning after three weeks of standoffs.
Demonstrators in the Mong Kok district launched a fresh assault early on Sunday, putting on helmets and goggles before surging forward to grab a line of metal barricades hemming them into a section of road.
Hundreds of police officers hit out at a wall of umbrellas that protesters raised to fend off police pepper spray. Protesters screamed and hurled insults and violent scuffles erupted before police surged forward with riot shields, forcing the protesters back.