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