Police in Hong Kong are hunting a girl, believed to be 12-14 years old, and her accomplices in connection with the audacious theft of a diamond necklace said to be worth HK$36 million (US$4.6 million) from a jewelery store in the city.

The heist took place on Friday afternoon, when the girl and her accomplices, two women and a man said to be between the ages of 30 and 40, entered the Emperor jewelry store in the high-end 1881 Heritage mall in the city's Tsim Sha Tsui shopping district.

While the women and man distracted staff by asking them to show them items, the girl stole a key from a drawer, opened a display case, and removed the 100-carat necklace, before leaving the store unnoticed, local media reported.

An image of the girl captured by mall security cameras was published by the South China Morning Post. Police say she may have changed clothes quickly after leaving the store, and added that border security in the territory were on high alert for the suspects, who they believe may try to flee the city.

The stolen necklace was 100-carat gold embedded with more than 30 diamonds. The gang had left the store before staff noticed that the item was missing, Sky News reported.

Police described the young suspect as "slimly built." She was dressed in black trousers, a blue shirt and a grey hooded top, when she was seen leaving the mall, AFP reported.