Giacomo Stucchi, a senator who chairs the parliamentary committee that oversees Italy's secret services, said Italian intelligence had played a key role in tracking down the jihadist known as Abu Nassim, a Tunisian national who was until recently reported to be leading a group of Isis fighters around the port of Sabratha in Libya.
"I would like to express my satisfaction over the anti-terrorist operation that has led to the arrest in Sudan of the Tunisian terrorist Moez Fezzani," Stucchi said, using Abu Nassim's real name.
Abu Nassim lived in Italy for most of his 20s. He subsequently fought in Afghanistan and Syria before reportedly moving to Libya in 2014.
He first arrived in Italy in 1989 to work on building sites. Suspected of trying to radicalize and recruit other Arab immigrants, he disappeared in 1997 and resurfaced in Pakistan, on his way to join the late Osama bin Laden's forces in Afghanistan.
He was arrested by US forces in 2001 and held at the Bagram airbase detention facility. From there he was was transferred to Italy in 2009 after prosecutors filed charges of terrorist recruitment related to his previous stay.
He was acquitted in 2012 and deported to Tunisia, only to be convicted on appeal in his absence the following year. By then he was already fighting in Syria.
Tunisia issued a warrant for his arrest in connection with the March 2015 Bardo Museum attack in Tunis, in which gunmen killed 21 tourists and a policeman.