A Dutch NGO said Tuesday it has launched an international effort offering pregnant women infected with the Zika virus free pills to trigger an abortion, aiming to halt any rush towards unsafe terminations.

"The Zika virus is now spreading to most of the countries where abortion is very restricted," Rebecca Gomperts, founder and director of Women on Web told AFP.

"We are extremely worried that this might cause increasing unsafe abortions. We really care about 's health and lives and we want to make sure that women have access to a good medical abortion."

The World Health Organization on Monday said a surge in serious birth defects in South America was "strongly suspected" of being caused by the mosquito-borne Zika virus and constituted an international health emergency.

It comes amid a regional surge in cases of microcephaly—a devastating condition in which a baby is born with an abnormally small head and brain.

Gomperts said women who feared their unborn child might be affected could contact the service on www.womenonweb.org for a free online consultation.

If there are no contraindications, then a package of pills to abort the foetus with instructions for use would be mailed to their home address.

A "medical abortion" is a combination of two different pills to trigger a non-surgical termination and can be used up to the 12th week of pregnancy, Gomperts said.

Women on Web was set up in 2005 to support access to safe abortions around the world, and currently answer about 10,000 emails a month from women seeking advice on a variety of issues.

Early action

Gomperts did not want to reveal how many medical abortion packages are sent each month, but she brushed aside any criticism saying: "Our goal is to save women's lives."

Women on Web is asking women to state if they are infected with Zika for research purposes, but say the organisation will "accept any reason that women have" for wanting an abortion.

WHO warned last week that Zika virus was "spreading explosively" in the Americas, and said the region could see up to four million Zika cases this year alone.

Brazil, which has become the worst affected country with some 4,000 suspected cases of microcephaly is also the world's largest Catholic country by population and places tight restrictions on abortion.

Brazilian authorities also intercept any packages which contain pills for a medical abortion, and Women on Web said it was calling on the government to suspend this "at least for the duration of the Zika epidemic."

The site also warns that postal services to other countries hit by Zika virus such as Colombia and Guatemala could take between one to five weeks.

"So it is important that women contact Women on Web as early as possible when they are aware of their Zika infection," the website says.