HONG KONG • The Hong Kong seller of luxury watches looked on in horror as masked men wielding the biggest sledgehammer he had ever seen smashed through the door of a neighbouring watch store, held a machete to the owner's throat, scooped up hundreds of thousands of dollars worth of timepieces, and then scattered into the city's maze of streets.

Less than two weeks later, armed robbers attacked again. This time, the watch merchants of Kowloon fought back.

Among them was the watch seller who witnessed the previous robbery. He said he grabbed an iron pipe he had handy for just such a confrontation and sprinted out to join the battle against the robbers who were smashing the front of Past & Future Times with hammers, trying to get to the store's high-end watches, while other gangsters brandishing machetes formed a menacing shield around them.

"I heard 'Boom! Boom! Boom!' People shouting," said the merchant, who asked to be identified only by his surname, Pan, because he feared for his safety. So much so that he now keeps a large meat cleaver in the drawer of his front desk and has protected his store with a new double door and toughened glass.

The robbers came at the merchants with their knives and then, seemingly scared off, ran away, he said. "All the shops came out to help. We're very united now," said Mr Pan.

They have to be. Hong Kong's 30,000-strong police force has been so stretched by a half year of anti-government protests that it is struggling to keep the peace.

Armed robbers and burglars are seemingly exploiting policing vacuums caused, in part, by the redeployment of officers to riot-control duties.

The police say the proud reputation of the semi-autonomous Chinese territory of 7.5 million people as an Asian haven of tranquillity, with crime rates lower than other cities its size, is being eroded.

"We used to be a very safe city six months ago, but somehow we face a lot of challenges," said Chief Superintendent Kwok Ka Chuen, a spokesman for the police force.

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Still, Hong Kong remains a city where visitors do not need to think twice about venturing out at night. It had six times fewer homicides last year than New York, seven times fewer burglaries and 88 times fewer robberies.

Ms May Chan said police patrols that used to walk the beat, morning and afternoon, past the Times watch store in Kowloon where she sells timepieces for tens of thousands of dollars, stopped abruptly in August after the protest movement picked up steam and radicalised.

The latest police figures appear to bear out the suspicions of store owners in Kowloon that the police do not have enough people.

In the first half of this year, the police recorded just 44 robberies - or about one every four days. But this soared to 126, close to one robbery per day, from July to last month as the protests and related violence increasingly stretched the force.

When compared with the same period last year, robberies increased by 147 per cent. Burglaries also increased in the past five months to 1,270, or eight per day, double the number for the same period last year.

Mr Pan, the watch seller, said police patrols are resuming again in his repeatedly robbed area of Kowloon, but in larger squads of around a half dozen officers because they fear being "hit with a petrol bomb or a brick" from violent protesters.

And if robbers do come back, the watch merchants are ready. He said they are hiring private security and have set up an alarm system so they can alert one another if attacked.

"We're all armed with weapons," he said. "I never believed it would happen in Hong Kong."

ASSOCIATED PRESS