A 13-year-old girl has been arrested in connection with an assault on a 15-year-old girl at the Kwun Tong Promenade in the early hours of New Year’s Day.

Police say the alleged attack occurred at around 1 am on Thursday.

Video of the incident has been circulating online, showing the alleged assault taking place as many bystanders looked on.

After reviewing extensive CCTV footage, officers arrested a 13-year-old girl in Kwai Chung.

Acting Chief Inspector Leung Sze-nok of the Kwun Tong Police District said officers believe the the victim was deliberately targeted.

"The victim and the arrested person know each other. The arrested person was dissatisfied because the victim had, on several occasions, [allegedly] spread untrue information about her online," she said.

"At the time of the incident, after the arrested person met the victim, she immediately resorted to violence against the victim, including repeatedly slapping and kicking her, causing multiple bruises to the victim's face and body.”

Police are urging parents to pay attention to their children's social lives and to maintain open communication.