UPDATE 9-Hong Kong protesters trash Xinhua agency office in night of violence
* Police fire tear gas at start of protests
* Protesters head to Central, vandalising metro, buildings
* China's official Xinhua news agency among firms targeted
* Violence some of the worst in recent weeks (Adds further Xinhua comment, changes headline)
By Clare Jim and Donny Kwok
HONG KONG, Nov 2 (Reuters) - Police fired tear gas at black-clad protesters across Hong Kong on Saturday after they set fire to metro stations and vandalised buildings including China's official Xinhua news agency in some of the worst violence to hit the city in weeks.
Earlier, police had also used tear gas in a downtown park where thousands of protesters - many angry at what they say has been a heavy-handed police response over five months of anti-government demonstrations - had gathered on a sunny afternoon.
Small groups of masked protesters then fled to the Central business district, through streets lined with banks and top-end jewellery and fashion stores, setting light to ramshackle street barricades and hurling petrol bombs as riot police and water cannon trucks closed in.
Protesters are angry at perceived Chinese meddling with Hong Kong's freedoms, including its legal system, since the city returned from British to Chinese rule in 1997. China denies the charge.
Just as a crowd of largely peaceful demonstrators finished making origami paper cranes in Chater Garden, a cricket pitch in colonial days, activists began throwing petrol bombs on the streets outside, in front of the headquarters of HSBC and the Hong Kong base for the Bank of China.
Police again responded with tear gas on what was the 22nd straight weekend of protests.
Protesters later set fire to entrances of metro stations -- often targeted as services close down to stop people gathering -- and hauled two telephone booths out of the ground to erect one of many flaming barricades. Cat-and-mouse clashes continued into the night as protesters retreated to the Causeway Bay area and across the water to the northern Kowloon side.
Some shops and businesses were also vandalised including an outlet of American coffee chain Starbucks and the offices of China's Xinhua news agency.
"The practice of the black rioters once again shows that 'stopping the violence and restoring order' is Hong Kong's most important and urgent task at present," a spokesperson for Xinhua said in a Facebook post, adding that its doors had been smashed and fire and paint bombs thrown into the lobby.
Hong Kong media associations also condemned the vandalism at Xinhua, one of the mainland's key symbols of presence in Hong Kong, calling for a halt to violence and urging police to handle the matter seriously.