Four Tunisians have been arrested in Italy on piracy charges, accused of seizing migrant boats in the central Mediterranean and taking their engines, leaving the vessels adrift.

According to investigators, the four men would identify boats transporting asylum seekers to Europe and, with the assistance of other vessels, blockade them in international seas off the Tunisian coast before boarding and robbing the passengers of money and phones and the boat of its engine.

One migrant described an attack: “They cut us off course as if they wanted to ram us. Then they boarded us. They were armed with knives and threatened us that if we didn’t give them the engine they would hurt us. We had no choice.”

The top prosecutor in Agrigento, Sicily, Salvatore Vella, said officials had become increasingly aware of apparent engine thefts. "We noticed that half of the small iron boats recently used by migrants leaving Tunisia to reach Europe and rescued by the Italian coastguard lacked engines."

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“This evidence matched what witnesses among the asylum seekers had told us, that they were attacked by Tunisian men who robbed them and stole their engine," adding that "We gathered as much information as possible, and we intervened at sea, arresting the men who operated on a fishing boat.”

What was on the boat?

On the boat, police discovered at least three stolen engines, as well as hundreds of euros and dozens of mobile phones. Because of the Montego Bay Convention, which permits all governments to intervene in the suppression of piracy on the high seas or in any other place outside the jurisdiction of any state, Italian police were permitted to carry out the arrests in international waters.

The Tunisians, who were apprehended on July 24, are being held in a Sicilian prison. Investigators are attempting to discover whether they were acting independently or on behalf of human traffickers.

Migrant crisis 

Migrants are attempting to traverse the Mediterranean Sea in perilous metal boats, making the journey much more hazardous. According to the UN, almost 20,000 people have died obn this route since 2014.

The vessels are mass-produced and soldered together. Asylum seekers claim that as soon as they reach the open sea, they begin to take on water. The repercussions for a boat's occupants are lethal if it also loses its engine.

Tunisia has eclipsed Libya as the primary migrant departure point. The maritime journey to Italy is the world's most dangerous, with NGOs describing it as a "liquid graveyard."

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On July 16, the EU approved a €1 billion (£860 million) accord with Tunisia to help curb irregular migration. Recently, Tunisia was accused of transporting hundreds of Sub-Saharan African migrants to a desert territory near the Libyan border.

Libyan border guards and humanitarian workers said they had rescued hundreds of migrants who had been abandoned in the desert by Tunisian authorities, with many left to perish in the intense heat.