The robbed flat is being rented by several young people who were university schoolmates who are now in business, work as civil engineers and one even striking it rich after starting a Japanese restaurant.

Police yesterday suggested the possibility that the Man Wah Building flatmates were targeted because of an extravagant lifestyle.

The building is several decades old, but the exterior of the robbed unit is striking with its huge windows.

The 600-700-square-foot unit serves as a "private party room" where the tenants frequently invite friends over to enjoy red wine, cigars and play poker.

People visiting the unit often don luxury watches worth hundreds of thousands of dollars.

Superintendent Chung Nga-lun of Kowloon West regional headquarters' crime unit said they received a report claiming a local criminal syndicate had plans to commit a robbery in the building.

Officers then planned an ambush.

Six men arrived in a taxi at around 6pm. Five entered the building disguised as deliverers and with knives hidden.

They tied up three men, aged 23 to 29, after managing to get in.

One of the victims, however, managed to tap on a neighbor's window and tell her to "call the police."

The woman who was having dinner did so, although officers were already at the scene.

They moved into action and quickly subdued the suspects, finding three knives, a telescopic baton, and stolen goods when the five came down to the lobby to get away.

The stolen items included HK$35,000 in cash, eight luxury watches, and a batch of phones and laptops.

The six robbers, aged between 18 and 43, were last night still in custody. The taxi they arrived in was stolen in Tsuen Wan and had fake license plates.