Hong Kong police have arrested seven people over robbery of six gold bars worth HK$7 million (US$893,102), with some suspects believed to have fled to mainland China.

The force said on Saturday that four men and three women were arrested on Thursday after a 36-year-old man reported the robbery at about 12.30am the same day at a car park at the airport.

According to the victim’s account, he had been hired by a Chinese businessman to transport six 1kg (2.2lbs) gold bars from Indonesia to Hong Kong. He was ambushed by three knife-wielding suspects wearing face coverings as he made his way to his car.

The suspects grabbed the man’s backpack containing the gold bars, injuring his thigh and arm in the process, before fleeing in a seven-seater car. The victim was taken to Princess Margaret Hospital.

Police traced the thieves using the city’s surveillance camera network and arrested seven individuals aged between 20 and 39. Some have triad backgrounds.

The force said it was still searching for the gold bars and stressed that the attack was not random.