An off-duty police officer was stabbed in Kwai Fong MTR station on Friday night.

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The stabbing of an off-duty officer by three masked men in Kwai Chung on Friday night (Aug 30) has been been condemned by Hong Kong's police chief as "despicable".

Three men armed with knives attacked the man in Kwai Fong MTR station, leaving him with four wounds to his back, right shoulder and arms, a spokeswoman from the police public relations branch said.

The victim was sent to Princess Margaret Hospital in Kwai Chung for treatment. Two of the masked trio were dressed in black and the other in grey.

The officer worked in the armoury of Kwai Chung's stores management division, according to sources.

He remained conscious but suffered bone-deep knife wounds. The suspects fled the scene through Kwai Fong MTR station.

Speaking after visiting the injured officer, Commissioner of Police Stephen Lo Wai-chung condemned the attack as "despicable".

"Ambushing a police officer in this open way is a despicable act. Police will pursue the case with the full force of the law. I also appeal to any eyewitnesses to get in touch with the force and provide information."

Lo said initial investigation showed the officer had not been involved in any arguments in his private life, but the force would not rule anything out when looking at the assailants' motives.

The case will be handled by the New Territories south regional crime unit.

The attack came on the eve of a banned rally organised by the Civil Human Rights Front, with anti-government protesters expected to take to the streets, and a sweeping wave of arrests of prominent pro-democracy activists and lawmakers earlier in the day.

Hong Kong has been rocked by months of street protests and political unrest, which stemmed from opposition to the now-shelved extradition bill that would have allowed transfers of criminal suspects to mainland China, among other places, to face trial.

This article was first published in South China Morning Post.