Officers said the suspect is aged between 30 and 35 and about 1.8 metres tall, and has light skin and black hair.
Officers also described him as “very violent”.
The force received a report at about 5am that a taxi driver was attacked at the intersection of Eastern Street and Queen’s Road West.
He was certified dead after he was rushed to hospital.
Assistant Western district commander Sin Kwok-ming said they found a pool of blood in the taxi, and initial investigations suggested the driver, 48, was attacked with a sharp object, leaving him with a wound that was 7-centimetre-long and about 2-centimetre-deep on his neck.
“As for the motive, we are not ruling out any possibilities, including if they had a quarrel before [the attack], or the attacker has mental health problems or is even violence-prone,” he said.
Officers seized a chopper which they believe was used in the attack.
Police also visited a hotel in the area as part of their investigation, trying to determine if the suspect was a resident there.