A case of Zika virus infection has been confirmed in Indonesia's Sumatra province amid global fears of a pandemic and as the World Health Organisation (WHO) is holding an emergency meeting on Monday.

Jakarta's Eijkman Institute for Molecular Biology said a 27-year-old man has been diagnosed with Zika virus during the institute's research on the dengue outbreak.

The Indonesian health ministry has not officially confirmed the report, Today Online reported.

The infected man had never travelled overseas, raising fears about the reach of the virus in a region where Zika virus infections has historically occurred.

"Out of the 103 (dengue-negative) specimens that we checked, we found one positive for Zika," the institute's deputy director Dr Herawati Sudoyo told Agence France-Presse.

"We concluded that the virus has been circulating in Indonesia for a while," Sudoyo said.

About two dozen countries in the south and Central America and several others in Europe and the rest of the world have reported Zika cases, and the number infections has been steadily growing.

In Brazil the virus has been linked to a foetal deformation known as microcephaly, in which infants are born with smaller-than-usual brains. The reported cases of microcephaly in Brazil have gone beyond 4,000.

WHO has said it expects as many as four million cases of Zika in the Americas.

The latest reports from Colombia, the second worst affected country after Brazil, said more than 2,000 pregnant women were infected, raising fears among pregnant women across the region.

In Singapore, authorities are closely watching the spread of Zika virus around the globe.

Mosquito-borne Zika virus has not been found in Singapore, but it has historically occurred in southeast Asia.

Medical experts had said last week Singapore is extremely vulnerable to Zika virus and that any outbreak will be far more serious than the current dengue crisis.

The ministry also issued guidelines to people travelling to countries where Zika has caused health emergency.