TRIPOLI (AFP) - Libya said on Sunday it will appeal to the International Criminal Court to reverse its decision to prosecute Saif al-Islam, a son of slain dictator Muammar Gaddafi.

"We will obviously appeal" as required within five days of the announcement of the decision taken on Friday, Justice Minister Salah al-Marghani told a joint news conference with Prime Minister Ali Zeidan.

"A team of Libyan and international experts are discussing the preparation of the appeal," he added.

On Friday, the ICC rejected a bid by Tripoli to halt its prosecution of Saif al-Islam for crimes against humanity committed while trying to put down Libya's 2011 armed uprising.

"The chamber concluded that it has not been sufficiently demonstrated that (Libya's) domestic investigation (covers) the same case that is before the court," the Hague-based court said in a summary of the decision.

Saif al-Islam, 40, is being held by a brigade of former rebel fighters in Zintan, 180km south-west of Tripoli, since his capture in November 2011, five months after the ICC issued a warrant for his arrest.

The court, which was mandated by the UN Security Council to investigate the Libyan conflict, has clashed with Tripoli over where he should be tried.

The North African country has been plagued by a security breakdown since the revolt, with abductions and other crimes taking place frequently, and the new government is still unable to control the former rebels.