The International Criminal Court chief’s prosecutor Wednesday called for the “immediate arrest and surrender” of Moamer Gaddafi’s son Seif al-Islam, who was reportedly set free by a militia in Libya.

Seif al-Islam, the second son and heir apparent of the late deposed Libyan dictator, was said to have been released on Friday by a militia that controls the town of Zintan in western Libya.

An arrest warrant issued by the Hague-based ICC against Seif in 2011 “remains valid and Libya is obliged to immediately arrest and surrender Mr Gaddafi… regardless of any purported amnesty law in Libya,” Fatou Bensouda said.

But the prosecutor general’s office in Tripoli, where a rival UN-backed administration is based, said the amnesty could not apply to Seif al-Islam because of the severity of his crimes, saying he was still wanted for a 2015 conviction.

Bensouda said the world war crimes court is now “verifying” Seif al-Islam’s whereabouts.

She called on Libya, the UN Security Council and “all other relevant” countries “to provide my office with any relevant information in their possession.”

The ICC also called for the arrest and surrender of Libya’s former security chief Al-Tuhamy Mohamed Khaled, who is wanted on similar charges as Seif for his role in attempting to quash the 2011 revolt against slain strongman Gaddafi.

The ICC in April unveiled an arrest warrant for Khaled.

“It is imperative for both suspects to be apprehended and immediately surrendered to the custody of the ICC so that their guilt or innocence can be established…for justice to be done, and seen to be done,” Bensouda said.