The Moroccan navy on Thursday blocked the Mediterranean harbour in which a controversial Dutch "abortion ship" was due to dock in the first such trip to a Muslim country, one of the organisers said.

"They have blocked the harbour. We can see a big warship in front of the harbour," Gunilla Kleiverga, a gynaecologist, told by phone from an apartment near the harbour of Smir, 40 kilometres (25 miles) east of Tangier.

"We're making an alternative plan," she said, without elaborating.

But access to the harbour was prohibited, because of "military manoeuvres," as there was a large police presence.

"The security forces arrived first thing this morning to block access" to the marina, said the caretaker of a residential building nearby.

At around midday, between 200 to 300 Islamists staged a protest against the visit.

Women on Waves, the Dutch group organising the trip, is seeking 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.

They have already set up a hotline.

Kleiverga said that, despite being illegal, around 700 abortions take place in Morocco every day, many of them exposing the women to dangerous and sometimes fatal treatment.

On Wednesday, in the first government reaction to the planned trip, the health ministry said the ship was not authorised to operate in Morocco and called on the relevant authorities to prevent it from doing so.

"The ministry ... has never been informed of this event and has not authorised any non-resident party or doctor in Morocco to carry out this medical intervention," it said.

"The ministry calls on the relevant authorities to do what is necessary to ensure that the law is applied," it added.

Local youth group the Alternative Movement for Individual Liberties (MALI), which helped organise the trip, said the authorities had informed Women on Waves of the decision to prevent the abortion ship reaching the harbour.

But Kleiverga insisted that the boat would not counsel or treat women in Morocco, hinting that it might transport women outside Morocco's maritime borders before doing so.

"We are only treating women in international waters. We're on a Dutch ship, where Dutch law applies. Of course we (will) adhere to Moroccan law, and we're not going to offer abortions in Morocco," she added.

MALI activist Ibtissam Lachgare said the group, which includes two abortion doctors, was awaiting the arrival of a Dutch woman MP at Smir.

In the past 11 years, a Women on Waves ship has visited Ireland, Poland, Portugal and Spain, sparking protests in each country from pro-life groups.

Rebecca Gomperts, the group's founder, said that illegal abortions cause the deaths of 78 Moroccan women each year on average, citing statistics provided by the World Health Organisation.

But Moroccan pro-life groups dispute those figures.

Ordinary Moroccans have voiced strong opposition to the visit.

"Moroccan law forbids abortion. Moroccan religious identity says it is forbidden and so does Islam. So the government cannot allow this ship to come to Morocco," lawyer Abdelmalik Zaza was quoted as saying in Al-Tajdid, the newspaper of ruling Islamist party the PJD.