Hong Kong police have arrested seven men over the robbery of nearly HK$1 million (US$129,000) in gold ornaments from a jewellery store in the New Territories last month.

Five suspects were detained in Tuen Mun and Tin Shui Wai over the past three days, and the other two were taken into custody late last month, the force revealed on Saturday. They are aged between 25 and 37.

The robbery took place on the night of June 16 and was caught on video that circulated online.

It shows four men wearing hoodies, masks and gloves storming into the Far East Jewellery shop at the T Town North shopping centre on Tin Wah Road in Tin Shui Wai, wielding sledgehammers and retractable batons.

According to Assistant District Commander Au Yeung Siu-kong, the robbers threatened staff with the weapons and used the hammers to smash glass display counters. The footage showed employees and the single customer at the time exiting the shop to gather outside as one of the thieves stood watch. Staff at the MaBelle jewellery store opposite had pulled down their shutters.

The gang stole HK$930,000 worth of gold ornaments in about 45 seconds and jumped into a car that sped off towards Lau Fau Shan.

Officers found the abandoned, torched car on Ha Tsuen Road. “No one was in the car but we found two hammers,” Au Yeung said, adding the vehicle had been stolen from Lok Ma Chau.

“After sweeping CCTVs and analysing intelligence, we targeted a triad group which hired locals as core members and mounted the arrests.”

The suspects were arrested over offences including robbery, arson and car theft. Two were released on bail, while the others were being held for further questioning. Police said the investigation was ongoing and additional arrests were possible.

According to official statistics, reports of robbery across the city increased about fivefold to 122 in the first three months of this year, from 23 in the same period last year.