A hospital source says investigations are underway but that the first case may have occurred early last month.
PIC: Zika virus is spread by daytime-active Aedes mosquitoes. (AFP)
Guinea-Bissau has recorded three cases of Zika, becoming the second country in West Africa where the dangerous viral disease has been detected, the government said on Saturday.
"Three cases of contamination by Zika virus have been confirmed," a statement quoted Health Minister Domingos Malu as saying.
The cases occurred in the Bijagos archipelago, a group of 88 islands of which 23 are inhabited, Malu told a cabinet meeting on Friday.
The communique gave no further detail about the three cases, their location or how the disease may have arrived on the Bijagos.
A hospital source told AFP that investigations were underway but the first case may have occurred early last month on Bubaque, one of the Bijagos islands.
A former Portuguese colony of 1.6 million people, Guinea-Bissau suffers from chronic poverty and instability.
Previously, the only other country in West Africa where Zika had been detected was Cape Verde, an archipelago in the Atlantic, where 7,500 cases have been recorded since October 2015.
Saturday's statement said the authorities were taking steps to prevent further spread of the mosquito-borne virus.
It announced that an anti-Zika commission had been set up, comprising several ministers under the authority of Prime Minister Baciro Dja.
Zika is benign in most people but has been linked to microcephaly -- a shrinking of the brain and skull -- in babies, and to rare adult-onset neurological problems such as Guillain-Barre Syndrome, which can result in paralysis and death.
In an outbreak that started last year, about 1.5 million people have been infected with Zika in Brazil, and more than 1,600 babies born with abnormally small heads and brains.