An international operation to rescue Muammar Gaddafi from his besieged last refuge involved mercenaries who had taken part in the notorious "Wonga Coup" led by former SAS officer Simon Mann, The Independent has learnt.

Crause Steyl, a pilot and one-time business partner of Sir Mark Thatcher, had taken part, along with the former prime minister's son, in the failed attempt to overthrow the dictator of oil-rich Equatorial Guinea. He was asked, just after the Libyan dictator's death, to fly stranded soldiers of fortune out of a mission "which had gone badly wrong". (He declined to help.)

The private force of South Africans are said to have undertaken the task of getting Gaddafi out of the country via the convoy in the belief it had the backing of the Western powers. The men were recruited, it is claimed, by a woman of British background – whose name cannot currently be published for legal reasons – living in Kenya and working on behalf of a company in London.

However, the extraction of Gaddafi ended in ferocious violence and confusion when the convoy carrying him out of Sirte, his birthplace where he made his final stand, drove into an ambush with sustained air strikes from French warplanes and ground attacks from rebel fighters. The venture came to a bloody end, with Gaddafi tortured and killed, and some of the South Africans with him reported killed, injured and captured. This has led to recriminations and accusations of betrayal. At least some of those taking part believe that the hidden aim of those who had hired them was not to save the former Libyan leader but to deliver him into the hands of his enemies.

Details of the South African involvement and the link of some of the former soldiers and policemen to the failed Equatorial Guinea plot seven years ago were revealed by Mr Mann after he had spoken to Mr Steyl. Included among those said to be attempting to get out of Libya, he was told, was a former South African soldier who was involved in the failed coup with both Sir Mark Thatcher, Margaret Thatcher's son, and Mr Mann.

Another group of mercenaries from the same contingent, meanwhile, are said to be "protecting" Saif al-Islam, Gaddafi's son, and a prominent, belligerent face of the regime during the civil war, who is reported to have fled to a region bordering Algeria, Niger and Mali.

Saif al-Islam is said to be negotiating with the International Criminal Court to hand himself in to face war crimes charges. However, there are also reports that his armed escort may be trying to move him outside the court's jurisdiction to Zimbabwe. Chief Prosecutor Luis Moreno-Ocampo said: "We have some information that there is a mercenary group trying to help him to move to a different country, so we are trying to prevent this activity. We are also working with some states to see if we can disrupt this attempt. Some of these mercenaries are South African, allegedly."

Mr Steyl's part in the Equatorial Guinea coup involved arranging a lease for a Boeing 707, which was eventually intercepted in the Zimbabwean capital Harare in the process of transporting arms to carry out the overthrow of President Teodoro Obiang Nguema. Mr Steyl, too, ended up giving evidence against Thatcher in court.

Mr Steyl stressed that he refused the mission to airlift 50 fighters out of Libya. Former Scots Guard officer Simon Mann, who has served prison sentences in Zimbabwe and Equatorial Guinea for his role in the attempted coup, said last night: "We are concerned about what may have happened to those who had been injured, who may have been arrested.

"I would personally like to help in any way I can, legally, to help get them out... These are people I knew and obviously I don't want to see them suffer. I hasten to add, of course, that I was not involved in any way in this Libyan operation."

Some of the South Africans captured by the Libyan rebels appear to have been treated with remarkable leniency. Captured regime mercenaries, the vast majority of them black sub-Saharan Africans, faced summary execution in the hands of revolutionaries. But some of the ones taken after the Sirte bombing were spirited away and even transported abroad for medical treatment.

Danie Odendaal, one of the fighters, claimed he was with Gaddafi when the convoy was attacked. He has told South African media that three groups of South Africans were flown in to Libya via Dubai and Cairo to help the Gaddafi family under a deal done with Nato.

The plan, he said, was initially to take Gaddafi to Niger. "We all believed they [certain Western countries] wanted him out of Libya. But then Nato attacked. It was a gruesome, gruesome orgy, I think we were sold out". The dictator suffered brutal abuse before being killed. "The poor thing screamed like a pig," he said. However, some rebels then helped the South Africans get away from the scene.

The Independent has learnt that Mr Odendaal, who was travelling on a Greek passport, was sent to Cairo to receive treatment for injuries he had received and has since moved to Western Europe.

However not all the mercenaries have been freed and Mr Odendaal has named two South Africans who were killed in the frantic confusion around Sirte. But the identities remain unverified and next-of-kin have not been informed.

Revolutionary fighters present at the time of Gaddafi's capture spoke of seeing bodies of white mercenaries which later disappeared. Abdullah Hakim Husseini, of the Misrata brigade, recalled: "There were, I think, three or four bodies of foreigners. We were told not to touch them, they would not be going back to Misrata... Later I heard they were from Zimbabwe and South Africa."

Mercenaries: key players

Danie Odendaal

Though it was widely reported that Colonel Gaddafi had recruited mercenaries to protect him as his regime unravelled, his hired guns were generally thought to be made up of poor sub-Saharan Africans. The revelation that his closest guards included three groups of more experienced former policemen and soldiers from South Africa is therefore striking – especially as Nato, the very force targeting Gaddafi's regime, has been implicated in assisting them to enter Libya. The information has come from Danie Odendaal, who says he was among the men protecting the dictator in the moments before he died, and had been hoping to smuggle him over the border into Niger. He claims that two of his fellow countrymen died in the final firefight that led to the capture and killing of the dictator. Mr Odendaal is now being treated in a North African hospital. It has been reported that the men were paid $15,000 (£9,300) for the operation, with interviews carried out in August – two months before Gaddafi was tracked down.

Crause Steyl