The government said earlier that half of the 115 cases reported previously were foreigners, mainly from China, India and Bangladesh, and most had already recovered. Many of them are believed to be among the hundreds of thousands of migrant workers in Singapore`s construction and marine industries.
Some new Zika cases have been found beyond the cluster area where the virus was initially detected.
"We have been tracking Zika for a while now, and knew it was only a matter of time before it reached Singapore," Prime Minister Lee Hsien Loong posted on his Facebook page. "Our best defense is to eradicate mosquitoes and destroy breeding habitats, all over Singapore."
Singapore is the only Asian country with active transmission of the mosquito-borne Zika virus, which in pregnant women can lead to serious birth defects.
Malaysia confirmed its first case of Zika infection, in a woman who had recently visited Singapore.
The United States, Australia and other countries have added Singapore to the growing list of places that pregnant women or those trying to conceive have been warned to avoid.
Meanwhile, in south Florida, where nearly 50 cases of Zika have been reported in non-travelers, officials said they trapped the first mosquitoes that tested positive for the virus, further confirming reports of local U.S. transmission.
"This find is disappointing, but not surprising," Florida Commissioner of Agriculture Adam Putnam said in a statement. "Miami-Dade County, the City of Miami Beach, and state and federal partners will continue to work aggressively to prevent the spread of Zika," Putnam added.
That work is likely to be seriously hampered by a hurricane expected to hit Florida overnight, as high winds will make aerial insecticide spraying impossible and standing water in its aftermath will provide added mosquito breeding sites.
The Singapore outbreak and travel warnings come just two weeks before the Singapore F1 motor-racing Grand Prix, a major sporting and tourist draw. The race promoter said planning for the event is going ahead "as per normal".
Singapore`s Tourism Board has said it is premature to consider any impact on the tourism industry, stressing the tropical city-state remains a "safe travel destination".
More than 55 million people pass through Singapore`s Changi airport each year. Tourism arrivals topped 8 million in the first half of this year, around 1 million more than a year ago.
China is trade-dependent Singapore`s top overseas market, and the Zika outbreak coincides with a dip in overall exports and slowing economic growth in both countries.
"If this continues, certainly it will have a negative impact, but it`s hard to quantify in percentage terms or dollar value," said Francis Tan, an economist at United Overseas Bank in Singapore.
The Zika virus, which has spread through the Americas and the Caribbean since first being detected in Brazil late last year, is generally a mild disease but can cause microcephaly, a rare birth defect that can lead to serious developmental problems, and has also been linked to other severe fetal brain abnormalities.
The World Health Organization has also linked Zika to Guillain-Barre, a rare neurological syndrome that causes temporary paralysis in adults.
The WHO, which declared Zika an international public health emergency, was holding a regular meeting of its Zika emergency committee on Thursday to review the spread of the disease.
Malaysia, which has two land border crossings with Singapore, asked those going to the city-state to use mosquito repellent and to cover up to avoid bites. Tens of thousands of people travel between the two countries daily.
Indonesia has also stepped up protective measures following the Singapore outbreak, intensifying checks on arrivals from Singapore and posting paramedics at airports and border checkpoints.
Zika is primarily spread by mosquitoes but can also be transmitted through unprotected sex with an infected person. A case of suspected transmission through a blood transfusion in Brazil has raised questions about other ways it may be spread.
Several companies and government agencies are working to develop vaccines against Zika. On Thursday, Japanese drugmaker Takeda Pharmaceuticals said it has joined the effort with help from U.S. funding, and it expects to begin human testing next year.
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