Over a dozen victims were targeted in a sacrificial killing on a packed immigrant boat sailing from Libya to Italy, reports the Daily Mail.
Survivors told of how the people were thrown overboard after the boat's engine failed in rough weather. Some Nigerian women among the passengers performed a "magic dance" and then pointed out victims to the captain. They were then hurled into the sea.
The ritual was allegedly intended to "cast out the devil" and "calm stormy seas."
"One man was taken down to the hold and beaten before being led back on deck and thrown in the sea with his hands tied," said Italian prosecutor Ignazio Fonzo.
"As this went on, prayers, chanting and dancing took place.
"This happened several time during the voyage. We believe at least a dozen people were thrown alive into the sea in this way," he added.
25 people were found dead from engine fumes in the hold on arrival at the Italian island of Lampedusa, a hot spot for illegal immigrants attempting to reach Europe from Africa.
Many more of the migrants needed hospital treatment for the effects of fumes, exhaustion and dehydration.
The men arrested all come from West Africa - where voodoo and spiritual rituals are often practiced - and were aged between 28 and 44.
More than 30,000 migrants have arrived in Lampedusa since the outbreak of the Arab Spring earlier this year. Many other have died in the attempt when their boats have sunk or capsized while making the crossing.