Respiratory samples of three travellers from Wuhan, the epicentre of the virus in China, were tested positive, reports Xinhua news agency.
The patients, in stable condition, were under isolation in hospital, according to the Centre for Health Protection (CHP) in Hong Kong.
Of the three new cases, the first is a 62-year-old woman, who arrived in Hong Kong by train on January 19 and developed fever and cough the next day.
Three of her family members, who travelled to to Hong Kong with her, will be transferred to Lady MacLehose Holiday Village for quarantine although they showed no symptoms.
The other two cases involved a couple from Wuhan, 62 and 63 respectively, who came to Hong Kong on January 22 and showed symptoms over following days.
The CHP is making epidemiological investigations and relevant contact tracing of the five confirmed cases in Hong Kong.
As of Friday noon, the CHP has received reports of 239 suspected cases and the five confirmed ones, with 122 cases discharged already after being ruled out as novel coronavirus infection.
The city's Chief Executive Carrie Lam said on Saturday that a high-level meeting on the pneumonia situation will be held later in the day.
Hong Kong has activated the serious response level in its contingency plan to prevent the spread of the infectious disease.
It has enhanced the monitoring of suspected cases, imposed a health declaration form system on inbound travellers by air and railway, and cancelled festive events for the Lunar New Year celebrations.
( With inputs from IANS )