The savagery of the attack on a man who was clearing a blocked road in Hong Kong shocked many who saw the viral video footage.

As the 53-year-old man sought to clear barricades being used to block the road in Mong Kok on Dec 1, an assailant came from behind and bashed his head with a metal drain cover. The impact was so great that the victim collapsed unconscious.

The assailants continued to taunt him and threaten him with more beatings even as he regained consciousness, with blood pouring down his face.

Almost a month later, the Hong Kong police said on Tuesday that they have arrested three people involved in the attack.

The trio were picked up separately - in Ap Lei Chau, Tsuen Wan and Central - after officers pieced together vital clues from various surveillance cameras.

The three suspects, aged between 33 and 34, all worked as interior designers, the South China Morning Post reported.

The police said that the man who used the metal object to hit the victim would face assault and unlawful assembly charges, while the other two would be investigated for assisting in the assault, as well as for unlawful assembly.

Two of the men apparently knew each other as they were seen walking to the scene together.

The victim, who is named only as Mr Liu, told state broadcaster CGTN earlier that he was fortunate he did not suffer a skull fracture even though his head wound needed 10 stitches.

He could not recall the moment when he was attacked.

"When I regained consciousness, I saw a large group of people standing around me.

"One of them wanted to attack me with an umbrella," he said.

He said he was merely doing what a normal person would do to help the city clear roads from being blocked illegally.

While he did not comment on his alleged attackers for hurting him, he wanted to ask radical protesters what they hoped to achieve by wreaking havoc on the city. "If you have destroyed the present society, what future does Hong Kong have?"