SOS Mediterranee, a non-governmental organization (NGO) that ran the migrant rescue boat Aquarius together with medical charity Doctors Without Borders (MSF), vowed on Friday to continue its work with a different ship next year.

On Thursday, the two NGOs said the ship was ceasing operations in the Mediterranean due to "sustained attacks" from European states.

"We are looking for new ships and are having talks with several shipping companies," Verena Papke, the director of SOS Mediterranee Germany, said in a press conference in Paris.

Pepke said the NGO will have found a new rescue ship by 2019 at the latest.

"The Aquarius was obviously a big symbol," but at the end of the day, it was only a ship and needs to be replaced, she added.

SOS Mediterranee and MSF stopped their mission in the wake of flag registration and legal problems, which according to the NGOs reflect growing hostility from European governments to migrant rescue work.

This year, Aquarius was twice stripped of its flag, last by Panama in October, leaving it unable to sail again after arriving at the French port of Marseille in early October.

Attempts by SOS Mediterranee and MSF to find a European government willing to re-register the boat have failed. Switzerland turned down a request on Monday.

Meanwhile, Italian prosecutors last month called for the vessel to be impounded on controversial charges of illegal disposal of dangerous waste material.

Part of the accusation was that clothing worn by migrants was disposed of as "special," rather than "toxic" waste, and could have been contaminated with HIV, meningitis and tuberculosis.

"The Aquarius [...] faces allegations of criminal activity – allegations which are patently absurd," MSF said in a statement on Thursday.

MSF said the vessel picked up nearly 30,000 people in international waters between Libya, Italy and Malta since it began its first rescue mission in February 2016.

In Italy, anti-immigration Interior Minister Matteo Salvini tweeted that the end of Aquarius' activities was cause for celebration, as it would lead to "fewer departures, fewer landings, fewer deaths."

Salvini, who leads the far-right League party, has banished charity-run migrant rescue ships from Italian ports, seriously limiting their ability to bring migrants ashore.

Alice Weidel, parliamentary group leader of Germany's far-right Alternative for Germany (AfD), also welcomed the end of Aquarius' operations.

"The end of the Aquarius is good news in order to regain control over the flow of migrants to Europe," she said.

"Despite recent efforts of other NGOs at sea, today there are no dedicated rescue boats operating in the Central Mediterranean," MSF said.

Salvini has justified his actions by claiming that rescue ships worked with human traffickers to bring migrants into Europe, a charge that charities have always rejected.

Around 1,300 refugees have died or gone missing this year in the central Mediterranean, according to the latest data from the International Organisation for Migration.

The figures are down from 2,853 for the whole of 2017. But the death rate has risen from 2.1 to 3.1 per cent, signalling that journeys have become more dangerous.

NGOs say this is due to the absence of charity rescue vessels.

Papke said she thinks that many deaths are invisible - especially if NGOs and other organizations aren't helping at sea and reporting on the situation can no longer be reliable.