One of them is a cargo flight crew member who was exempted from quarantine.
The man, 36, arrived from the United States on Monday and returned to his home in Yau Ma Tei before he tested positive for the virus.
The Centre for Health Protection said residents living in the same building as the man had been tested for Covid-19 and no cases had been found.
They are required to get tested six more times, the centre said.
It added that 20 close contacts of the man have been sent to a quarantine camp.
The other two Omicron cases involve a man who flew in from Ghana and a man who had been to the Bahamas and the United States.
They tested positive at the airport.
Meanwhile, the centre reported five new imported Covid-19 cases on Saturday.
They involve people who flew in from the United Kingdom, Canada, Nepal and Nigeria.
All of them were asymptomatic. Three of them are double jabbed while two of them have been triple jabbed against the virus.