Italy's justice minister has strongly defended the government's decision to free and repatriate a Libyan warlord wanted by the International Criminal Court.

Italy's justice minister said on Wednesday Rome had no choice but to free a Libyan military officer wanted for war crimes by the International Criminal Court because of what he described as mistakes and inaccuracies in the court's arrest warrant.

Italy's government Wednesday blamed its much-criticised release of a Libyan war crimes suspect on the International Criminal Court (ICC), which it accused of presenting a poorly written arrest warrant.

Rome's decision to release Osama Almasri Najim drew condemnation from Italian opposition parties, NGOs and the ICC.

Migrants expressed their dismay and sense of betrayal on Wednesday over Italy's decision last week to release a Libyan policeman wanted by the International Criminal Court (ICC) for war crimes and human rights abuses and allow him to return home.