The city's silent majority broke silence on Sunday to voice against violence after Hong Kong's law enforcement agency foiled several attempts over the past few days by radicals to use dangerous chemicals and explosives in the anti-government protests.

These include testing of bombs by three radicals who were arrested at the scene by the police on Saturday, and discovery of hazardous items at a university on Friday and two home-made bombs in a secondary school on Monday.

In the eyes of Angelo Giuliano, a consultant who has lived and worked in Hong Kong for three years, what recently happened in the city is "terrorism".

When protesters began to beat up those with differing views, they went too far from the "freedom" and "democracy" that they protested for, he said.

"People like me, like foreigners (in the city) should speak out and tell the rest of the world what is the reality of Hong Kong," Giuliano said, explaining why he participated in the assembly.

"It is important that people come out and start to say, 'stop the violence'," Giuliano said.

He is one of tens of thousands of residents who rallied at Tamar Park in Admiralty to express their support to police for enforcing the law and maintaining peace and order in Hong Kong.

Some of the victims took the stage to speak out against violence.

Chan Ho-lap, 37, a construction worker, was attacked by radicals at Tin Shui Wai subway station on Sept 1. He was beaten up by radicals who overheard him telling police officers maintaining order at the station that he supported them. He said he found it unbearable to listen to the radicals hurling insults at the police officers on guard at the station and their family members.

"I don't understand why I am not even free to say I support the police," said Chan. The experience made him realize that violence does not bring freedom. It only infringes on other people's freedom.

Harry Hung, a student, said violence will never be an acceptable option to achieve goals and express own opinions.

The 17-year-old said some teachers were organizing strikes and protests, which is unacceptable as they are supporting what is illegal and wrong.

The mass rally came a day after the city's law enforcement agencies arrested three men, aged between 27 and 40, for testing explosive devices and chemicals in a secluded area of Tuen Mun district, New Territories.

Police seized a series of tools used in the test, including a radio-controlled detonation device, a gas mask and a bulletproof steel plate. It was believed they intended to use them during public processions.

Senior Superintendent Steve Li Kwai-wah said that based on intelligence and initial investigation the police believe there are two reasons behind the test: to upgrade the power of explosive devices and to launch attacks during assemblies and rallies in the future.

Slamming the "irresponsible" acts, Li said they endangered residents' lives.

Saturday's seizure is the second time that a bomb plot was foiled within a week. Last Monday, the police defused two home-made bombs containing 10 kilograms of explosives in a secondary school in Wan Chai, Hong Kong Island.

Bomb Disposal Officer Alick McWhirter said had the devices been set off, a large number of people would have been killed and injured.

On Friday night, a month after the City University of Hong Kong was vandalized by radicals, police found 34 gasoline bombs, 20 smoke bombs, 12 corrosive bombs and a number of flammable items after the university staff reported having seen "suspected dangerous items" on the campus.