Seif al-Islam making a statement in Zintan following his arrest Libyan Prime Minister designate Abdel Rahim El-Keeb said on Monday he was yet to verify whether former spy chief Abdullah Al-Senussi was captured. \"Before I can confirm it to you , I would like to confirm to myself that he was indeed captured. I will not confirm it to you until I am 100 percent sure,\" he told a news conference.
A spokesman for Libya\'s interim administration, the National Transitional Council (NTC), said on Sunday local officials in the desert town of Sabha had confirmed the capture of Muammar Gaddafi\'s intelligence chief Senussi.
That came a day after Gaddafi\'s son Seif al-Islam was captured in the same region.
An NTC military official also said on Sunday that Senussi had been surrounded at a house owned by his sister.
Meanwhile, the interim prime minister announced that the formation of a new Libyan government will be made public tomorrow.
The new government, which had been due to be announced on Sunday, was to have been delayed by 48 hours at the most, NTC vice chairman Abdel Hafiz Ghoga earlier told reporters.
UK Foreign Secretary William Hague has also urged that Seif Al-Islam be prosecuted under international standards even if his trial takes place in Libya and not at the International Criminal Court (ICC).
Hagues\'s statement came as ICC chief prosecutor Luis Moreno Ocampo was due in Tripoli for talks over the fate of the former dictator\'s one-time heir apparent, who was captured at the weekend.
Information minister Mahmoud Shammam however has insisted the trial will take place on home soil and not at The Hague after news of the arrest on Saturday sparked a wave of celebrations across the country.
But concerns have emerged that the former rebel faction that captured him is refusing to hand him over to the authorities in Tripoli, raising further doubts about the chances of a fair trial.
Former intelligence minister Abdullah al-Senussi who has been wanted for brutally repressing Libya\'s recent pro-democracy protests has also been captured alive, Tripoli said.
Asked if he backed the domestic trial decision, Mr Hague told BBC Radio 4: \"I would like to see him tried to international standards, whether that be in Libya or in The Hague. That is the important thing.
\"The details of that have to be sorted out between the ICC and the transitional government.\"
He added: \"Of course, it is within the rules of the International Criminal Court that people can be tried within the country concerned, by agreement with the ICC.
\"They also have every right to try Seif Al-Islam for any crimes committed before February, before the indictment of the ICC.\"
World powers, fearful that Seif would not be given a fair trial after his father was felled by a bullet to the head after being captured exactly a month ago, are urging Libya to work with the ICC.
The court wants to try the 39-year-old for crimes against humanity allegedly committed by Gaddafi\'s forces in crushing anti-regime protests in February.
But the NTC insists that Seif will face a fair trial at home.
\"The decision is that he will be tried by Libyan courts. It is a question of national sovereignty,\" NTC vice chairman and official spokesman Abdel Hafiz Ghoga told reporters.
Interim justice minister Mohammed Al-Allagui earlier told AFP Gaddafi\'s son would be tried in Libya \"because local justice is the rule and international justice is the exception\".
\"We have the necessary guarantees for a fair trial, especially after the amendment of a law that guarantees the independence of the judiciary as regards the executive,\" he said.
On Saturday, the ICC said Libya must hand Seif over but held out the prospect of a trial in Tripoli.
ICC spokesman Fadi Al-Abdallah told AFP Libyan authorities were obliged to cooperate with the ICC and surrender him to the court as required by the UN resolution on Libya.
\"If they want a trial in Libya, they must submit a request for dismissal and procedures in Libya must be conducted on the same charges as those contained in the warrant of the ICC,\" Abdallah added.
Asked about the ICC\'s comments, Allagui said: \"We will reach agreement with the ICC, in conformity with the laws in force.\"
On Sunday, Abdallah said the ICC had not yet been officially notified of Libya\'s position on the issue.
\"According to the principle of complementarity and the Statue of Rome, the priority rests with national law,\" he said.
 Ex-spy Senussi was captured in the south on Sunday, officials said.
Bashir Uweidat, who heads the southern Wadi Shati military council, said Senussi \"did not put up any resistance\" and was arrested by former rebels in his sister\'s home in the Al-Guira region.
Ghoga confirmed the arrest of Gaddafi\'s brother-in-law, who is also wanted by the ICC.
The court issued warrants on June 27 against Seif, 39, Gaddafi and Senussi on charges of crimes against humanity.
In particular, it accused Senussi, 62, of being an \"indirect perpetrator of crimes against humanity of murder and persecution based on political grounds\" committed in Benghazi.
Senussi has been described by the ICC as \"one of the most powerful and efficient organs of repression of Muammar Gaddafi\'s regime\".
He is also wanted in France where a Paris court sentenced him in absentia to life in 1999 over an attack on a French UTA airliner a decade earlier that killed 170 people.
World powers have repeatedly urged Libya\'s new rulers to respect international norms in dealing with prisoners amid reports of abuse, and are now urging the NTC to cooperate fully with the ICC.
Zintan military council chief Osama Juili said Seif would be held there until a new transitional government decides his fate.
\"At the moment, he is being held in Zintan. We are going to guarantee the treatment of prisoners under international law,\" Juili said.
In a new video posted on Facebook on Sunday, Seif Al-Islam Gaddafi said he was in Zintan among his “brothers” and his “people” and that he was facing “no problems”.
Seif Al-Islam was captured near the southern town of Obari by NTC fighters from Zintan who brought him on an airplane to their town, where he was being held in an unknown location.
News of Seif\'s capture was greeted with celebratory gunfire in Libya\'s major cities and Senussi\'s arrest was described as a \"victory\" by the interim defence minister.