The middle-aged man got on a route 87D bus, causing police to board several buses on the same route to check all passengers but by 9 pm there was no sight of the robber.

The superintendent of West Kowloon crime unit, Alan Chung Nga-lun, said the man entered a bank on Nathan Road at 3.38 pm yesterday.

He handed a note in Chinese to a female bank teller that said he was carrying out a robbery before threatening her with a black gun he held in both hands and pointed at her. "Robbery! I have a gun and give all the money to me," the note said.

The man gave the women a black bag and asked her to put cash in it. She handed over HK$14,000 in cash. The process took about 30 seconds.

Chung said the teller tried to give chase when the robber walked out of the bank but failed.

She saw the robber run across the street and get on a bus headed toward Sham Shui Po.

Officers with bulletproof vests and guns soon arrived at the scene, stopping 87D buses near the junction of Nathan Road and Argyle Street in Mong Kok to search for the robber but without success.They also set up roadblocks on Argyle Street and at Lion Rock Tunnel to search every bus and at bus stations.

Chung said police officers are also contacting the bus company to check the CCTV footage inside the bus to track down the whereabouts of the robber.

But Chung said the police cannot tell whether the gun carried by the robber was real or not because he didn't shoot.

Chung also revealed the man in his 40s is about 1.75 meters tall and has a strong build.

He was wearing a dark blue jacket, black trousers, dark-colored sneakers, a black face mask, a black hat and a pair of sunglasses.