Police have launched a massive manhunt for up to six men who they say escaped with a HK$28 million ($3.6 million) ransom in one of the biggest kidnapping cases in Hong Kong in recent years.

The men are said to have seized the daughter of a billionaire at her luxury home at Clear Water Bay after a break-in and robbery on Saturday.

Police said the kidnappers are from the mainland. Two are aged between 26 and 29 and were wearing dark jackets, bluejeans and sports shoes. One has a scar on his right palm. Another two are 1.6 meters tall and wore white coats.