Fishermen at a Tunisian port on Sunday prevented a ship carrying far-right anti-immigration activists from docking, dealing a fresh blow to a controversial mission aimed at disrupting the flow of migrant boats from north Africa to Europe.

Faced with the prospect of being blocked by the fishermen in Zarzis, the ship, the C-Star, moved up the Tunisian coast, and was expected by opponents tracking its path to try to land at either Sfax or Gabes on Monday.

Chartered by extremist group "Generation Identity", the C-Star passed through waters off Libya on Saturday.

It briefly tailed the Aquarius, operated by French group SOS Mediterranee, one of several NGO boats conducting search and rescue operations in an area notorious for deadly migrant boat sinkings.

Having left Cyprus on August 1, the 40-metre (130-foot) C-Star needs to land in Tunisia for supplies but appeared to have been caught off guard by the strength of opposition among local fishermen, as well as rights groups.

"If they come here we'll close the refuelling channel," Chamseddine Bourassine, the head of the local fishermen's organisation, told AFP.

"It is the least we can do given what is happening out in the Mediterranean," he added.

"Muslims and Africans are dying."

An official at the port, who asked to remain anonymous, said: "What? Us let in racists here? Never!"

- 10,000 dead -

The C-Star headed straight from Cyprus to Libyan waters after being discouraged from attempting to dock en route in Greece and Sicily, with authorities concerned about the prospect of protests.

The self-styled "Defend Europe" mission has not got off to the best of starts.

Their boat was held up for a week in the Suez Canal by Egyptian authorities looking for weapons.

Then, after it landed in the Cypriot port of Famagusta last month, several of its crew jumped ship and asked for asylum in Europe -- exactly the kind of thing the mission was set up to prevent.

The C-Star crew say their main goal is to expose collaboration between NGO rescue ships and the traffickers who launch boats from Libya packed with migrants.

Humanitarian groups say Generation Identity is engaged in a publicity stunt and that any attempt to turn migrant boats back to Libya would be potentially very dangerous and illegal under international law.

Since the start of 2014, some 600,000 people from Africa, the Middle East and South Asia have been rescued from traffickers' boats and taken to Italy.

Over 10,000 have died en route and serial sinkings have resulted in privately funded or charity-run boats joining a multinational search and rescue operation coordinated by Italy's coastguard.

NGO boats have rescued around one third of the nearly 100,000 people picked up this year, but their relations with Italy have become strained as pressure to stem the flow of migrants has mounted.

- Squalid camps -

Critics say the NGOs make it too easy for the traffickers to guarantee would-be migrants safe passage to Europe, allegedly fuelling the lucrative trade.

Italian authorities last week impounded one NGO boat, the Iuventa, which is operated by German association Jugend Rettet.

They accused its crew of being in direct contact with traffickers to organise pick-ups of boatloads of migrants from locations very close to the Libyan coast.

On Sunday, the Aquarius was on hand to help as an Italian coastguard patrol boat rescued around 100 people from a distressed dinghy.

The number of such rescues in international waters has fallen sharply over the last five weeks to under half the level of the same period last year.

Italian officials are cautiously optimistic that this reflects a breakthrough in their efforts to strengthen the Libyan coastguard's capacity to combat traffickers.

The Libyan navy told AFP that the coastguard, which has received training and new equipment from Rome, had intercepted six trafficker boats carrying a total of 1,015 people since Thursday.

Rights organisations have voiced concern over the focus on sending boats back to Libya, where migrants who fail to get to Europe often end up in detention in squalid camps where they risk torture, sexual violence and forced labour.

Italian officials defend the strategy as the only way to end a humanitarian crisis that is threatening to overwhelm the country's asylum system.

The crisis has also caused strains in Rome's relations with its EU neighbours, who have blocked migrants landing in Italy from travelling further north.

Source: AFP