Police officers fire tear gas during a protest in Hong Kong, China August 31, 2019. REUTERS/Tyrone Siu Tyrone Siu | Reuters

Hong Kong police fired tear gas and water cannon on Saturday and pro-democracy protesters threw petrol bombs in the latest in a series of chaotic clashes that have plunged the Chinese-ruled city into its worst political crisis in decades. Police fired round after round of tear gas and protesters took cover behind umbrellas between the local headquarters of China's People's Liberation Army and the government. Protesters also threw bricks dug up from pathways at police. The water cannon unleashed blue-dyed water, often used elsewhere to make it easier for police to identify protesters. Riot police then marched on foot toward the neighboring Admiralty district, followed by 20 police cars, where protesters had thrown fire bombs from flyovers, some landing close to police. Others shone blue and green lasers at police lines.

HONG KONG, CHINA - AUGUST 31: A protesters walks in front of a burning barricade after clashing with police at an anti-government rally on August 31, 2019 in Hong Kong, China. Chris McGrath | Getty Images News | Getty Images

There were unconfirmed reports of an off-duty policeman being wounded. In the neighboring Wanchai bar and restaurant district, police fought running battles with protesters, beating them with truncheons. There were several arrests. "We don't know how to stop this, how to stop the violence," said Celia Liu, who offers emotional counseling to protesters, as she watched riot police form a barrier across one of the world's busiest shopping districts, Causeway Bay. "... The young are emotional and we just can't stop it." The protests, which at one point blocked three key roads, came on the fifth anniversary of a decision by China to curtail democratic reforms and rule out universal suffrage in Hong Kong, a former British colony that was returned to China in 1997. "The government today said rashly embarking on political reform again will further polarize society, which is an irresponsible act," the government news.gov.hk website said. "It noted any discussions on constitutional development have to be premised on the legal basis, and be conducted under a peaceful atmosphere with mutual trust in a pragmatic manner." The People's Liberation Army on Thursday rotated its troops in Hong Kong in what it said was a routine operation. Their Hong Kong HQ was the former base of the British military garrison. Senior Chinese officials have warned that if the turmoil persists, "the central government must intervene".

Protesters throw tear gas canisters back at police during an anti-government rally outside of Central Government Complex on August 31, 2019 in Hong Kong, China. Anthony Kwan | Getty Images News | Getty Images

Hand signals

Thousands took to the streets of the Asian financial hub for a largely peaceful, meandering rally in the afternoon rain. Many of them joined a "Christian march" from Wanchai and congregating next to the Legislative Council, stormed by activists in an earlier protest. Other protesters, many wearing black and face masks, marched in Causeway Bay. The crowds grew after dusk in Wanchai, where demonstrators built roadblocks and banged iron sticks. Firemen battled a huge blaze outside a Methodist church in the main Hennessy Road where water cannon moved in. It was the same pattern all evening. Police advanced steadily, protesters retreated. Pedestrians yelled out "black cops", "gangsters" and "get fucked" as police passed.

A protester throws a brick during clashes with police outside the Central Government Complex during an anti-government rally on August 31, 2019. Chris McGrath | Getty Images News | Getty Images

There were also standoffs in North Point and Fortress Hill, to the east of Causeway Bay, and police fired tear gas at fire-bomb throwing protesters over the harbor in Tsim Sha Tsui. Police were targeting MTR subway trains to make arrests, with TV footage showing people being beaten as they cowered on the floor behind umbrellas. The protests have gone on for three months, sometimes turning violent, and have targeted the airport, the legislature and the Liaison Office, the symbol of Chinese rule. Police arrested a number of prominent pro-democracy activists and three lawmakers on Friday, seeking to rein in a movement that began with anger over planned legislation allowing extraditions to mainland China, where courts are controlled by the ruling Communist Party. It soon broadened into calls for democracy amid fears China is squeezing Hong Kong's freedoms. But the latest protests have no leaders. The slogan is "be like water", meaning be flexible. Marchers on Saturday were marching here and there, wherever streets took them, communicating with different hand signals and chanting "stand with Hong Kong" and "fight for freedom".

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