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 city back to China in 1997 entered its fourth week with no sign of a resolution despite talks scheduled 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 late August that effectively denies the financial hub the full democracy the protesters are demanding for an election in 2017.
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"Unless there is some kind of breakthrough in two hours of talks on Tuesday, I'm worried we will see the standoff worsen and get 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 Beijing-backed leader Leung Chun-ying, who has so far resisted calls to quit, said more time was needed to broker what he hoped would be a non-violent end to the upheaval.
"To work out a solution, to put an end to this problem, we need time. We need time to talk to the people, particularly young students," he told Hong Kong's ATV Television. "What I want is to see a peaceful and a meaningful end to this problem."
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.
Roughly a thousand 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.
Police smash protester umbrellas
Scores of riot police had smashed batons at a wall of umbrellas that protesters raised to defend themselves. Amid shouts and hurled insults, violent scuffles erupted before police surged forward with shields, forcing the crowds back.
One activist in a white T-shirt and goggles was hit with a flurry of baton blows, leaving him bleeding from a gash in the head. Several protesters were taken away.
Dozens of people were reportedly injured in the two nights of clashes, including 22 police officers. Four people were arrested early on Sunday, police said.
The clashes came hours after the talks were confirmed for Tuesday. They will be broadcast live.
On Sunday evening, crowds again began building as protesters stockpiled helmets and fashioned home-made forearm shields out of foam pads to parry baton blows.
The protesters, led by a restive generation of students, have been demanding China's Communist Party rulers live up to constitutional promises to grant full democracy to the former British trading outpost.
Hong Kong is ruled under a "one country, two systems" formula that allows it wide-ranging autonomy and freedoms and specifies universal suffrage for Hong Kong as an eventual goal.
But Beijing is wary about copycat demands for reform on the mainland and it ruled on Aug. 31 it would screen candidates who want to run for the city's chief executive in 2017. Democracy activists said that rendered the universal suffrage concept meaningless. They are demanding elections with open nominations.
Leung appears hamstrung, unable to compromise because of the message that would send to people on the mainland while more force looks likely to only galvanize the young protesters.
Police say protesters becoming 'radical'
Hong Kong's Security Chief Lai Tung-kwok said some of the clashes in recent days had been initiated by activists affiliated to "radical organizations which have been active in conspiring, planning and charging violent acts."
The city's embattled police chief, Andy Tsang, also expressed his frustration when he broke three weeks of silence on Saturday to say "extremely tolerant" policing had not stopped protests becoming more "radical or violent."
The demonstrations pose one of the biggest challenges for China since the crushing of a pro-democracy movement in Beijing in 1989.
The situation in Hong Kong surfaced in weekend talks between U.S. Secretary of State John Kerry and Chinese State Councillor Yang Jiechi in Boston.
A senior State Department official said Hong Kong was discussed as part of "candid exchanges" on human rights while a Chinese Foreign Ministry statement said Yang had told Kerry that Hong Kong was "purely an internal affair of China".
In Mong Kok, protesters resting during the day on Sunday were defiant and also angry that local officials were portraying their campaign as increasingly radicalized and violent.
While police took down some banners and posters, they left one of the more popular and dramatic, a cardboard cut-out of Leung being hanged in effigy from a lamp-post.
"I will continue to stay here until CY (Leung) resigns," said Lap Cheung, 40, who quit his IT job in the United States to return to Hong Kong for the protests, adding that he had no hope for Tuesday's talks.
Besides Mong Kok, about 1,000 protesters remained camped out at the headquarters of the civil disobedience "Occupy" movement on Hong Kong Island in a sea of tents on an eight-lane highway beneath skyscrapers close to government headquarters.