Seventeen Nigerian survivors of a 2017 migrant boat sinking have filed a case with the European Court of Human Rights accusing Italy of violating their human rights by subcontracting their rescue to the Libyan coast guard.

The case, backed by a consortium of legal and human rights organizations, poses a direct challenge to Italy's much-touted 2017 deal with Libya that has greatly reduced the number of asylum-seekers reaching Europe.

Consortium members told a press conference Tuesday that the policy, which involved using EU funds to train and equip the Libyan coast guard to patrol its coasts and bring migrants back, had subjected would-be refugees to slavery, torture and other degrading and inhuman treatment.

They said Italy was responsible for the abuses because it maintained "effective control" over the Libyan rescuers.