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

International court demands answers after Italy released Osama Elmasry Njeem, who is accused of abusing detainees.

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.

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

Some opposition politicians have alleged the suspect was sent home to avoid jeopardising relations with Libya.

The government attributed the release to procedural reasons. But critics say it is because Italy depends on Libya to stem the flow of migrants from Africa.

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.

Italy's government has 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.

Prime Minister Giorgia Meloni of Italy announced on Tuesday that she was being investigated by Italian prosecutors for her alleged role in aiding and abetting the release last week of a Libyan official wanted on war crimes charges.