The other two cases have no known links to any existing cluster but the authorities did not specify where these cases were located from.
In his first public remarks on the outbreak, Prime Minister Lee Hsien Loong said on Thursday: "We must assume that Zika is elsewhere in Singapore".
Zika is a serious viral disease which can cause microcephaly in the newborns if contracted by pregnant women.
Since reporting its first Zika infection, Malaysia has increased insecticide spraying to kill mosquitoes.
Scientists trying to predict the future path of Zika say that 2.6 billion people living in parts of Asia and Africa could be at risk of infection, based on a new analysis of travel, climate and mosquito patterns in those regions.
"This patient has not been to any other country where large number of cases had been reported".
But nearly daily downpours, average temperatures of 30 degrees Celsius (86 degrees Fahrenheit), large green areas and a population of more than five million people packed in a city that is half the size of Los Angeles, which has a population of 4 million, make Singapore a hospitable area for mosquitoes.
Zika virus has been spreading across South and Central America since early 2015 and has now emerged in Florida, researchers said. "Mosquito-borne disease is something that we are going to have to manage for many years to come".
Dr Subramanian said the Health Ministry was of the view that the patient's death was not directly related to Zika.
While the reference material will undergo formal World Health Organization review in October, the agency has given the go-ahead for the strain's use given the urgent need of medical products to diagnose and treat Zika, researchers said. Dengue is not spread by sex, like Zika, but mosquitoes are responsible for the vast majority of Zika cases globally.
Wong Sin Yew, an infectious disease physician at Gleneagles Medical Centre in Singapore, said it was unclear for now whether Zika would become as widespread as dengue.
The ministry is also considering sending confirmed cases home to recuperate, but the infected persons are advised to take precautions to prevent themselves from getting bitten by mosquitoes, Khor said while attending a community outreach event in western Singapore on Sunday morning.
Singapore already has strict "no breeding" regulations for outdoor areas.
Total number of Indians infected with Zika virus in Singapore is now 15.
Even if Singapore could contain the spread of Zika, its status as an global trade and transit hub puts it at risk of further infections.
The 61-year-old was only the country's second confirmed Zika case.