Libyan leader Muammar Gaddafi's son Seif al-Islam, for whom the International Criminal Court issued arrest warrants for crimes against humanity, is in detention, the ICC prosecutor said.

"I have received confidential information stating he has been arrested," Luis Moreno-Ocampo told AFP.

Earlier, the chairman of Libya's rebel National Transitional Council told Al-Jazeera television from Benghazi he had "information that Seif al-Islam has been captured".

"He is being kept in a secure place under close guard until he is handed over to the judiciary," Abdel Jalil said, without giving a date or place for the reported capture of Gaddafi's son.

Before the revolt which erupted in February, Seif al-Islam was increasingly seen as the successor to his father, despite publicly ruling out any dynastic ambitions in the North African country.

He long served as the face of the regime in the West as he appeared in suits and ties and spoke fluent English.

Another of Gaddafi's sons, Mohammed, was also reported to have been captured.