Rome, Italy – Italian police said Thursday that 12 fellow passengers were thrown overboard by Muslims who were among migrants trying to get from Libya to Italy in a boat this week. According to police in Palermo, Sicily, 15 people were arrested by Italian authorities on suspicion of murdering the Christians at sea.

On Tuesday, the original group of 105 people left Libya in a rubber boat. Police said that some time during the trip north across the Mediterranean Sea, the alleged assailants – Muslims from Senegal, Mali and the Ivory Coast – threw the 12 overboard. Palermo police said that other people on the voyage told the authorities that they themselves were spared “because they strongly opposed the drowning attempt and formed a human chain.”

An Italian navy vessel intercepted the boat and transferred the passengers to a Panamanian-flagged ship. Police said that the Panamanian ship docked in Palermo, Sicily on Wednesday, after which the arrests were made. Police also revealed that the 12 who died were from Ghana and Nigeria.

Each year thousands of people make the dangerous sea journey from North Africa to Europe’s Mediterranean coast, often aboard vessels poorly equipped for the trip. Many of them attempt the voyage to flee war and poverty in Africa and the Middle East. According to the Italian coast guard, more than 10,000 people have arrived on Italian shores from Libya since last weekend alone.