The top UN human rights official called on Friday for countries with the Zika virus to make available sexual and reproductive health counselling to women and uphold their right to terminate pregnancies.

"Laws and policies that restrict her access to these services must be urgently reviewed in line with human rights obligations in order to ensure the right to health for all in practice," UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said in a statement.

The virus has been linked to microcephaly, a condition that leads to babies being born with small heads and birth defects.

His spokeswoman, Cecile Pouilly, asked about countries such as El Salvador that criminalize abortion, told a news briefing: "That's why we are asking those governments to go back and change those laws because how can they ask these women not to become pregnant? But also not offer them first information that is available but also the possibility to stop their pregnancies if they wish so."

The World Health Organization this week declared the Zika virus a global emergency.

Meanwhile, South Pacific kingdom of Tonga said Friday it has a Zika epidemic after five people tested positive for the virus and another 265 are suspected of having it.

The Centers for Disease Control and Prevention said in addition to Tonga, the Pacific islands of American Samoa and Samoa have also reported Zika outbreaks and it is warning Pacific travellers to protect themselves from mosquitoes, which spread the virus.

Tonga Health Minister Dr. Saia Piukala told The Associated Press on Friday the Zika outbreak is the island's first and it is awaiting the results of more blood tests that have been sent overseas. He said many people aren't being tested because of the cost, but are being diagnosed anyway because of their symptoms.

Piukala said there haven't been any reported cases of pregnant women contracting the virus.

"We hope that the pregnant women out there who have signs and symptoms of Zika come forward," he said.

Malinoa Fainu, from Ha'ateiho village, said she'd heard about the disease on television and is trying to take precautions.

"I'm afraid that I might catch it in my condition," she said. "I'm pregnant."

Of the five confirmed cases of Zika that originated in Tonga, three were discovered in New Zealand when people who had travelled to Tonga were tested, officials said. But New Zealand officials say there is virtually no threat of Zika there because New Zealand doesn't have the species of mosquito which is spreading the disease.

Brazilian researchers suspect the explosive spread of Zika is linked to an increase in the number of babies born with abnormally small heads, although scientists have not proven a link.

With files from The Associated Press