The cartel allegedly used voodoo rituals and promises of jobs to lure migrants to Italy, before getting them to work as prostitutes.

The Associated Press quotes the police in Catania, Sicily, as saying that the victims, including some minors, paid as much as 25,000 euros (($28,000) each to make the dangerous journey from Nigeria to Libya and then across the Mediterranean Sea to Italy.

Before leaving Nigeria, the migrants were subjected to a ritual that involved taking an oath of silence. They also agreed not to flee, and to pay back the cost of getting to Europe.

The suspected traffickers made upwards of 1.2 million euros (about $1.4 million).

The arrested Nigerian suspects include five men and five women. Four more people are on the run and are still being trailed by the authorities.

The organizers of the ring made sure that the women did not pay their “madams” or bosses in Italy directly.

Instead, money was wired to either the recruiter or their families in Nigeria, who then paid off the local recruiters.

The police said they identified 20 victims of the ring, which had divisions in Nigeria, Libya, Italy and other European countries.

The suspects are facing possible charges of criminal association with the aim of trafficking, aiding and abetting illegal immigration and exploitation by prostitution.

Police say the transnational nature of the crime makes it weighty, adding that the women were psychologically threatened throughout the voodoo ritual.

Trafficking in persons has been going on for years. Most of the trafficking from Nigeria is perpetrated in the southern state of Edo.

Smugglers have taken advantage of Libya’s lawlessness to organize migrant crossings to Italy and other parts of Europe.

According to Italy's Interior Data Ministry, 5,472 illegal migrants have arrived the country so far this year.

According to the International Organisation for Migration (IOM), 20,000 Africans--a chunk of them Nigerians-- have died in the Mediterranean Sea while attempting to make the perilous trip from Libya to Europe, since 2014.