HONG KONG -- Hong Kong police said on Monday that 21 officers were injured during the violent incidents over the weekend as radical protesters intensified violence, vandalizing shops randomly and assaulting police officers with deadly weapons.

Among the 21 officers, 16 were injured on Sunday, with one suffering massive bleeding after poled by a sharpened item in his back and five others were injured on Saturday after hit by bricks, according to a press briefing of the police.

Mak Chin-ho, assistant commissioner of police, said protesters used deadly weapons, including bricks, metal poles, long sticks and petrol bombs, to assault police officers.

"These attacks are intentional, planned and organized," he said.

"Through the whole of afternoon on Sunday, a large gang of rioters threw numerous self-made petrol bombs at police officers in Tsuen Wan," Mak said. "In certain incidents, they randomly threw petrol bombs from height at people on protest sites, hitting innocent passersby."

Besides assaulting police officers, radicals also obstructed roads and vandalized shops and tunnel facilities.

"Their destructive acts are rampant and reckless. They are not to be tolerated by any civil society," Mak said.

Elaborating on police officers forced to draw guns and one firing a warning shot to the sky, Mak said the officers were attacked and chased down by over 100 violent protesters armed with offensive weapons, a situation where their lives were in great danger.

"One officer fired a warning shot into the air. No one was hit," Mak said. "I must emphasize 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."

During the violent incidents on Sunday, 45 men and nine women, aged 12 to 51, were arrested for offenses including unlawful assembly, possession of offensive weapon and assaulting police officers. The number of the arrested protesters totaled 86 during the whole weekend.

Mak reiterated zero-tolerance to violence and said the police will continue to stand firm and carry out their duties faithfully, diligently and impartially. He appealed to residents not to remain silent and not to tolerate such radical acts but raise their voice against violence and cut ties with all rioters.

The police also arrested and prosecuted another suspect involved in assaulting a reporter from the Chinese mainland on Aug. 13 at Hong Kong International Airport. The man, charged of unlawful assembly, wounding, possession of offensive weapon and unlawful imprisonment, was on court Monday.