* Protesters fire bows and arrows at police, wounding one
* Violence at universities some of the worst in months of protests
* City on edge amid five months of demonstrations (Recasts; adds Mong Kok violence, paragraph 8)
HONG KONG, Nov 17 (Reuters) - Hong Kong protesters shot bows and arrows, wounding a policeman in the leg, and hurled petrol bombs from a barricaded university campus on Sunday, with activists braced for a possible final police clearance after fiery clashes overnight.
Police fired blue-dyed liquid from water cannon after several protesters fired arrows from rooftops at the Hong Kong Polytechnic University amid some of the most dramatic scenes in over five months of protests in the Chinese-ruled city.
Protesters stripped down to their underwear, before being hosed down by colleagues with fresh water.
Police said a media liaison officer was hit in the leg by an arrow. He was taken to hospital for treatment.
Huge fires had lit up the sky at the university in the heart of Kowloon district overnight as protesters hurled petrol bombs, some by catapult, and police fired volleys of tear gas to draw them on to the open podium of the red-brick campus.
After a few quiet hours as protesters slept on lawns and in the university library, police fired fresh rounds of teargas shortly after 10 a.m. Activists threw petrol bombs in return, some igniting trees outside the campus.
Chinese soldiers dressed in shorts and T-shirts, some carrying red plastic buckets or brooms, emerged from their barracks on Saturday in a rare public appearance to help residents clear debris blocking key roads.
Clashes also broke out on the artery of Nathan Road in the Kowloon district of Mong Kok, a frequent venue for unrest,
As fresh violence erupted on Sunday, Chinese soldiers in a base close to the university were seen monitoring developments with binoculars, some dressed in riot gear with canisters on their chests.
Parts of the campus looked more like a fortress with barricades and black-clad protesters manning the ramparts with improvised weapons-like bricks, crates of fire bombs, and bows and arrows at the ready.
"We are not afraid," said a year-three student Ah Long, who chose not to disclose his full name. "If we don't persist, we will fail. So why not (go) all in," he said.
The campus is the last of five universities to remain occupied, with activists using it as a base to continue to block the city's central cross-harbour road tunnel.
The presence of China's People's Liberation Army (PLA) soldiers on the streets, even to help clean up, could stoke further controversy over Hong Kong's autonomous status at a time many fear Beijing is tightening its grip on the city.
Hong Kong did not request assistance from the PLA and the military initiated the operation as a "voluntary community activity", a spokesman for the city's government said.
Pro-democracy lawmakers condemned the PLA's actions in a joint statement, warning that under the city's Garrison Law the military must not interfere in local affairs unless it is asked by the government to help with disaster relief or public order, government-funded broadcaster RTHK reported.
The Asian financial hub has been rocked by months of demonstrations, with many people angry at perceived Communist Party meddling in the former British colony, which was guaranteed its freedoms when it returned to Chinese rule in 1997.
Beijing denies interfering and has blamed the unrest on foreign influences.
Clashes between protesters and police have become increasingly violent, posing the gravest popular challenge to Chinese President Xi Jinping since he came to power in 2012.
Xi has said he is confident the Hong Kong government can resolve the crisis. Until Saturday, Chinese troops in the city had remained inside their base during the protests.
Chinese troops have appeared on Hong Kong's streets only once since 1997, to help clear up after a typhoon in 2018. (Additional reporting by James Pomfret, Joyce Zhou, Kate Lamb and Tom Lasseter; Writing by Greg Torode and Nick Macfie; Editing by Sam Holmes)