Two sons of fugitive Libyan leader Col Muammar Gaddafi were holed up in the town of Bani Walid until Saturday but have now left, says the head of the country's interim authorities.Mustafa Abdul Jalil told the BBC that Saif al-Islam and Mutassim Gaddafi had been blocking the town's surrender.Earlier, rebels said negotiations for Bani Walid's surrender had broken down and an assault was imminent.But Mr Abdul Jalil said the talks would continue until a deadline on Saturday.Meanwhile, a senior anti-Gaddafi commander is demanding an apology from the UK and the US over his capture and torture in Libya in 2004. AdvertisementMustafa Abdul Jalil: "Gaddafi sons had been blocking surrender of Bani Walid"Their role has been revealed in CIA papers found when offices and prisons in Tripoli were captured by anti-Gaddafi forces belonging to the National Transitional Council (NTC).Details of the case of Abdel Hakim Belhaj are included in messages sent to the Gaddafi government by US and British intelligence services.Relations between Col Gaddafi's government and China have also been revealed.Other documents found in Tripoli show Chinese arms manufacturers held talks as recently as July with Gaddafi government officials who were seeking arms and ammunition, Canada's Globe and Mail newspaper reported.The colonel's representatives visited Beijing, a Chinese foreign ministry spokeswoman said, but no contracts were signed and no shipments were made.A UN embargo on such sales was in place at the time.