A Somali man who colluded with Libyan smugglers to torture and extort fellow migrants in squalid prisons has been arrested in Italy as the refugee crisis continues to worsen.

Police on the island of Lampedusa said the 23-year-old suspect, Mohamed Ahmed Taher, “revelled” in beating asylum seekers and may have killed at least two people.

Giovanni Minardi, who led the team which detained Taher, told the Ansa news agency that Taher was part of a transnational armed criminal organisation dedicated to human trafficking, kidnapping, sexual assault, murder and illegal immigration.

Migrants who identified Taher as a torturer employed at a detention centre in Libya’s south-eastern region, Kufra, told prosecutors that after making the boat journey across the Mediterranean Sea on 27 May he attempted to threaten them into silence.

Migrants being held by Libyan forces in Tripoli (AFP/Getty Images)

“On my arrival, Mohamed the Somali was already in the [centre’s] structure,” said one victim.

“He beat the migrants. He revelled in humiliating us and throwing his weight around.

“I remember once the Libyan man, who owned the camp, had to tell him off because he was beating us so badly that it was killing people.”

Taher is accused of beating migrants with rubber hose, burning them with petrol and threatening with them with weapons.

As in similar past cases, police said asylum seekers were sometimes tortured while traffickers spoke to their relatives on the phone to pressure them into paying for their freedom and safety.

At least two people who attempted to escape the camp were reportedly beaten to death, while those fleeing other Libyan detention centres have been shot and killed.

Taher is the sixth person detained in Italy since March on suspicion of torturing migrants in Libya, where smuggling gangs have set up a ruthless trade amid the chaos of the country’s ongoing civil war.

Italian coastguard rescues refugee boat from Libya in the Mediterranean

The UN has warned of migrants being bought and sold at “slave markets” and being detained in official and unofficial prisons where they are raped, tortured, starved and held to ransom by armed gangs.

Survivors have told The Independent of being sold from one “owner” to another while being forced into manual labour, with those asking for wages or struggling with the work killed.

The centre in Kufra is part of a smuggling chain stretching from the Libyan coast, which is the main launching point for refugee boats towards Europe, back through Sudan to sub-Saharan African nations.

The Sahara is thought to be the deadliest zone for migrants, with 52 people dying in Niger after being abandoned in the desert by smugglers last week and many more being murdered or killed by thirst, hunger or falling off overloaded trucks.

The vast majority of asylum seekers currently making treacherous sea journeys to Europe are from African nations including Guinea, Nigeria, the Ivory Coast and Gambia, as well as Bangladesh, Syria and Iraq.

More than 85,300 migrants have arrived over the Mediterranean so far this year, with more than 2,000 dying in the attempt.

The bodies of at least 25 people who drowned off the coast of Libya were found near Tripoli on Tuesday after being washed up on a beach in a state of decomposition.

Members of the Libyan Red Crescent recover bodies of migrants washed ashore near Tripoli, Libya, on 27 June (EPA)

Almost 8,900 migrants were rescued off the Libyan coast on Sunday and Monday alone, after apparently being launched en masse in overcrowded fishing boats and smugglers’ dinghies.

Save the Children’s Vos Hestia was among the ships taking part in the huge operation, rescuing 1,065 people including a woman who gave birth on board.

She and her child were evacuated by helicopter to receive medical treatment in Malta, alongside two other pregnant women.

All ships at the scene of continuing rescues on Tuesday reported that they were full, even as new migrant boats were spotted approaching on the horizon.

Rob MacGillivray, Save the Children's director of search and rescue, said the charity’s vessel had seen a “massive increase” in rescues since last year.

“There’s no indication that there’s going to be a decrease, which makes it all the more important that there’s a joined-up European response to guarantee people safe passage and their status when they arrive,” he told The Independent.

“The NGOs can only deploy what they’ve got and they have limited capacity.”

Mr MacGillivray called the Mediterranean Sea “one of the largest unmapped graves in European history”, calling on politicians to change a narrative seeing migrants increasingly demonised as rescuers are accused of worsening the crisis.

NGO rescue ships, naval vessels, Frontex assets and commercial ships are being deployed by Italian commanders who are coordinating operations in international waters from Rome.

The EU has been attempting to increase cooperation with the fragile Libyan Government of National Accord (GNA) to reduce crossings, handing over millions of euros and equipment including new patrol boats.

In pictures: A day of refugee rescues in the Mediterranean Sea Show all 7 1 /7 In pictures: A day of refugee rescues in the Mediterranean Sea In pictures: A day of refugee rescues in the Mediterranean Sea A baby being taken on to MSF's Bourbon Argos ship from a boat carrying 130 migrants and refugees Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A refugee boat carrying 101 people being rescued by MSF's Bourbon Argos Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A refugee boat carrying 101 people being rescued by MSF's Bourbon Argos all images by Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A baby among refugees on a boat carrying 185 people off the coast of Libya Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea Migrants and refugees sleeping after being rescued by MSF's Bourbon Argos ship Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A crew from MSF's Bourbon Argos ship rescuing a boat carrying 130 migrants and refugees off the coast of Libya, at sunrise Lizzie Dearden In pictures: A day of refugee rescues in the Mediterranean Sea A woman in a stretcher being lifted onto MSF's Bourbon Argos ship from a boat carrying 130 migrants and refugees off the coast of Libya Lizzie Dearden

But the push has been condemned by the UN and human rights groups warning that any move to force refugees back to war-torn Libya, where they face torture and death, is a violation of international law.

The number of refugees crossing the Aegean Sea from Turkey to Greece has fallen dramatically since the EU-Turkey deal was imposed in March last year, seeing anyone arriving on islands detained under threat of deportation.

Migrants are also journeying into Europe by land, including via the Spanish enclaves of Ceuta and Melilla which border Morocco, and over the border between Turkey and Bulgaria.

Around 400 asylum seekers attempted to enter France through woods from the Italian town of Ventimiglia on Sunday, being tear-gassed by Italian police as their French counterparts used dogs to hunt down anyone who made it through.

Médecins Sans Frontières (MSF) said it was concerned for the welfare of at least 100 migrants who had been sleeping near a river in Ventimiglia and disappeared on Monday, with a 16-year-old boy known to have died while washing his clothes there.

Italy, which is housing more than 190,000 asylum seekers in state-funded accommodation, has criticised other European countries for failing to resettle asylum seekers and help rescue efforts.

“I’m sorry that not everyone, including in Europe, has shown the same willingness to take people in [as Italy has],” Prime Minister Paolo Gentiloni said in a message marking World Refugee Day last week.