SOS: Diehards hold out at Hong Kong campus as foreign pressure rises

Dozens of pro-democracy protesters stood firm within a besieged Hong Kong university on Wednesday, where an "SOS" sign was laid out as supporters took up calls to distract police surrounding the campus by disrupting city transport.

The four-day standoff between demonstrators and police at Hong Kong Polytechnic University (PolyU) rippled overseas, with the UN's human rights office urging a peaceful resolution, while the US senate passed new legislation supporting protesters' demands.

The epicentre of nearly six months of increasingly savage anti-China protests has shifted to the PolyU campus, a stone's throw from the city's harbour, where hardcore protesters have held off riot police with Molotov cocktails, bricks and arrows.

The confrontation has been the most intense and prolonged in nearly six months of unrest that began over a now-shelved bill to allow extraditions to China, which revived fears that Beijing was slicing into the city's freedoms.

Millions of angry citizens have hit the streets in a movement that snowballed into wider calls for free elections and an inquiry into alleged police brutality, demands that Hong Kong's Beijing-appointed leaders have rebuffed.

Protesters at PolyU said around 50 of their number remained after hundreds had fled deteriorating conditions and officials warned that police may fire live rounds.

Exhausted bands of youths continued to wander the debris-strewn campus, preparing Molotov cocktails while others slept on a gym floor.

A large "SOS" sign was laid out across an open courtyard, apparently intended to be viewed from above.

A 20-year-old protester who gave his name as Ken said food and water were running low.

"We will die because they don't let me out. Some people want to get out but they cannot. So we left this SOS," he told AFP.

The holdouts included around 20 of the university's students, a PolyU official said.

Hong Kong's chief executive Carrie Lam called Tuesday for protesters to surrender, adding that those over 18 would face rioting charges, but minors would not be arrested.

"I don't ever give up. Yes, I will fight until the end," said a 15-year-old holdout armed with bow and arrow who identified himself as William.

"But... it's very dangerous, because when you use the bow, the police must shoot you, with some unknown bullets. Maybe real bullets." Others were medically evacuated overnight, and on Wednesday before dawn AFP journalists watched as police chased down and arrested around a dozen students making a break for it.

Police said that since the siege began nearly 900 people at the campus had turned themselves in as of Tuesday night.

The UN human rights office was watching the university situation with "deepening concern", spokesman Rupert Colville said in Geneva.

Colville acknowledged protesters' "deep-seated grievances" but condemned the "extreme violence" of some demonstrators and called on authorities to seek a peaceful resolution.

A "Blossom Everywhere" strategy of disruptive vandalism lasting more than a week has brought much of the city's transport network to a standstill and shuttered schools.

Some of the busiest subway lines were disrupted yet again on Wednesday, with huge queues of commuters in the morning as protesters reportedly blocked train doors from closing.

Police said 213 people were charged in court on Wednesday with rioting for one of the diversionary actions earlier this week. The charge carries a maximum of ten years in prison.

But online protest appeals again brought citizens to the streets in some places Wednesday.

The city's education bureau reopened primary and secondary schools on Wednesday after a suspension that began last week. Kindergartens remained closed.

China has repeatedly condemned protesters as violent criminals and rejected any foreign criticism.

But the US Senate on Tuesday unanimously adopted new legislation threatening to revoke the favourable trade status that the semi-autonomous Chinese territory enjoys with the United States if its freedoms are quashed.

Lawmakers also approved a measure that would ban sales of tear gas, rubber bullets and other equipment used by Hong Kong security forces.

Beijing shot back on Wednesday, warning of "strong countermeasures" if the bill becomes law, and summoning acting US charge d'affaires William Klein to lodge a protest.

Hong Kong on Sunday holds district elections to its legislature, half of which is directly elected, the other half stacked with pro-Beijing lawmakers.

But Chief Secretary Matthew Cheung warned Wednesday that further violence could "ruin" the chances of holding the polls, in which China-aligned candidates are expected to take a drubbing.