HONG KONG - The government and police have condemned Sunday night's (Aug 25) violent clashes that left at least a dozen injured and many more arrested, even as law enforcers defended the firing of a warning gunshot - the first time a live bullet was released since anti-government protests started in March.

Assistant Commissioner of police operations Mak Chin Ho yesterday (Aug 26) said they arrested 86 people over the weekend, with the youngest aged 12 and oldest aged 52.

He said they were caught for offences including unlawful assembly, assaulting officers and possession of offensive weapons. A total of 21 officers sustained injuries.

Police said they fired 215 tear gas canisters, 72 rubber bullets, 44 sponge rounds and four bean bag rounds during the weekend clashes.

In a briefing, Mr Mak addressed the uproar over Sunday night's incident when six officers fighting off protesters in Tsuen Wan had little choice but to draw their pistols with one officer firing a warning shot to the sky as their lives were threatened.

The officers involved are from the Emergency Unit of New Territories South and were deployed to contain extremely violent protesters who had vandalised shops and entertainment venues in Yi Pei Square in Tsuen Wan at about 8pm.

"Over 100 rioters armed with offensive weapons surrounded and attacked our officers," said Mr Mak, who added that the officers' protective gear was smashed.

"They charged at our colleagues with road signs, metal poles and long sticks repeatedly and recklessly. As a result, our officers sustained multiple serious injuries."

At one point, one officer fell "but rioters still charged at him brutally" in a "clear intention to take his life", he pointed out.

The six officers then held up their revolvers as a precautionary measure.

"I must emphasise the officers demonstrated great restraint. Their use of force was indeed necessary and reasonable. It was to protect any person, including our officers themselves, from death or serious bodily injury," said Mr Mak.

In a separate briefing, the Chief Secretary for Administration Matthew Cheung said he was deeply saddened by the violent scenes.

Despite repeated explanations by the government that the "smart lamp posts" that can monitor traffic flow and the weather were not used to spy on citizens, protesters went on to cut them up on Saturday in Kwun Tong, he said.

Mr Cheung said the police - the city's strongest line of defence - have been very restrained in handling the protests, adding that the government is determined to bring the culprits to justice.

Security expert Clement Lai, who was a superintendent in the Hong Kong police, said police officers on the island are not trained to fire warning shots to the sky, but are trained to fire their revolver or any other sidearms to protect themselves and other members of public from death or serious injury.

He said the officers in Tsuen Wan had no choice but to the draw their weapons as they were outnumbered.

But they still needed to avoid harming the mob and others at the scene.

"(So the officer) quite rightly decided to fire a warning shot to the sky as it was the only option he had there and then. As a result, no attacker or members of public were shot.

"Instead, a police officer was stabbed with a knife.

"Their decision to draw their firearm as a precautionary measure was fully justifiable and in accordance with the 'Use of Force' principle," explained Mr Lai, who runs security consultancy Clement Shield.

Dr Lawrence Ho of the Education University of Hong Kong said while it is "legitimate" for police officers to draw their guns, and even fire a warning shot in an emergency, the specialist in public order management said "it is not common to use the firearm, even in a riot", as such a move would escalate the situation.

"In policing protests, officers would not use lethal arms if the purpose is to disperse and even arrest people in the crowd," Dr Ho added.

The Hospital Authority said 38 people were taken to the city's hospitals following the clashes. It added that 20 of the patients have been discharged, and the conditions of 17 others have stabilised. However, one male patient is in a critical condition.

TVB later reported that the number injured and sent to hospital had climbed to 41.

Police commissioner Stephen Lo on Sunday night visited some injured officers at Princess Margaret Hospital and said in a statement that the force "will strive to investigate all violent acts that have caused serious and even life-threatening injuries".

The developments come on the 12th weekend of brutal clashes between anti-government protesters and riot police, following brief respite during the 11th weekend which saw peaceful protests.

Violent clashes on Sunday took place after an approved march from Kwai Chung Sports Ground, where a national flag was removed and trampled on, to Tsuen Wan Park.

Some protesters deviated from the original route during the procession, blocked roads, confronted the police, and wantonly attacked officers with items like bricks and iron rods before hurling petrol bombs at police vehicles and officers in a street battle in Tsuen Wan.

Most retreated when the police rolled in the water cannon vehicles - the first time the cannons have been used, with jets of water directed at barricades put up by protesters.

Sunday's protests also spread to other areas including Sham Shui Po, Tsim Sha Tsui, Wong Tai Sin and the Kowloon entrances of the Cross-Harbour Tunnel.

On Saturday, radical protesters wracked havoc in Kowloon Bay, Wong Tai Sin and Sham Shui Po after an approved march in Kwun Tong.

Yesterday, four protesters aged 21 to 33 faced rioting or unlawful assembly charges for their alleged link to Saturday's violence.

Hong Kong has been roiled in unrest for three months since anti-extradition demonstrations escalated from June 9.

The protesters' five key demands are for the government to fully withdraw the highly divisive extradition Bill that is now suspended indefinitely; to have an independent inquiry into alleged police brutality; removal of June 12 protest as a riot; amnesty for those arrested and the implementation of universal suffrage.

Yesterday, some 40 protesters held a sit-in demonstration at Revenue Tower in Wan Chai to press the government to accept the demands of extradition bill opponents.

In an interview with RTHK, pro-democracy activist and Occupy movement co-founder Benny Tai suggested the government grant amnesty to both the hundreds of anti-extradition protesters arrested so far and also police officers who have abused their powers while on the front line.