A Dutch sailing boat offering abortions has arrived in international waters off Mexico's west coast, according to the organisation which operates it.

The vessel, which operates often in defiance of some countries' laws, took up position on Friday off Guerrero state on Mexico's southern Pacific coast.

Women on Waves, a non-profit group, said in an online statement that it was offering "free legal medical abortions till nine weeks of pregnancy" to women who needed them. It said its ship "has all required permits" and would receive women until Sunday.

It noted that Mexico permits abortions in cases of sexual violence. Abortion is limited in other cases to different degrees across the 31 Mexican states.

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In a media conference given in the Mexican coastal town of Ixtapa, Women on Waves president Rebecca Gomperts said access to safe abortions was a matter of "social justice" in Latin America, especially after the Zika crisis which increases the risk of birth deformities.

On board the Dutch boat, women are given abortion pills and remain under observation for a few hours before returning to shore on small vessels. The female crew does not perform surgical abortions.

The abortion pill, also known as a medical abortion, combines two medicines - mifepristone and misoprostol - that induce a miscarriage.

Recommended by the World Health Organization (WHO) as a safe and effective way to terminate pregnancy, every year around 26 million women worldwide use this drug combination, the WHO says.

Botched abortions

According to the WHO, around 47,000 women die from botched abortions each year, accounting for almost 13 percent of maternal deaths worldwide.

Women who do not live in Mexico City, where abortion has been legal since 2007, along with women who cannot afford to travel to the capital risk their lives by having illegal and often unsafe abortions, rights groups say.

"It's absurd that according to geography, where women live in Mexico determines ... if they can access a legal and safe abortion," said Regina Tames, head of Information Group on Reproductive Choice (GIRE), a Mexican women's rights group.

Tames said women in predominantly Catholic Mexico who want to end their pregnancies struggle to access a legal abortion because doctors are often unwilling to carry out the procedure or they have not been trained.

"Access to abortion in cases of rape is really quite limited," Tames told Reuters news agency.

The Women on Waves group has previously sent its ship to waters off Guatemala, Ireland, Morocco, Poland, Portugal and Spain.

The boat's last voyage in February to Guatemala sparked controversy after it was detained by Guatemala's army and expelled without carrying out a single pregnancy termination.

In October 2012, the Moroccan navy blocked the ship from entering the port of Smir.

Women on Waves said it had been invited to Morocco by a youth group called Alternative Movement for Individual Freedoms to inform women about how to induce "safe legal medical abortions," offer the necessary medication and start a discussion on legalising the practice in Morocco.